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 Pinnacle  Day:  6th - 7th  HCF and LCM 
 HCF and LCM 
 LCM  (Least  common  multiple)  of  two  or 
 more  given  numbers  is  the  least  number 
 that is exactly divisible by each of them. 
 HCF  (Highest  common  factor)  of  two  or 
 more  numbers  is  the  greatest  number 
 that  divides  each  of  them  exactly.  HCF  is 
 also  known  as  the  ‘Highest  common 
 Divisor’  (HCD)  and  the  Greatest  Common 
 Measure (GCM). 
 The concept of multiples and factors 
 If X , Y , and Z are three natural ?
 numbers and X × Y = Z , then 
 (i).  X and Y are called the factors of 
 Z. 
 (ii). Z is said to be divisible by X and 
 Y. 
 (iii). Z is said to be a multiple of X 
 and Y. 
 Example:  The  set  of  positive  Integers 
 which  are  factors  of  18  is  (1,  2,  3,  6,  9, 
 18). 
 Basic Concepts of  H.C.F. and LCM 
 Method of finding  H.C.F. 
 To ?nd the HCF of the given numbers 
 1.  Break  the  given  numbers  into  their 
 prime factors. 
 2.  The  HCF  will  be  the  product  of  all  the 
 prime  factors  common  to  all  the 
 numbers. 
 Let  us  learn  the  process  of  ?nding  HCF 
 with the help of some solved examples. 
 Example:- 
 Find the HCF of 96, 36 and 18 ? 
 Solution:- 
 96 =  2  ×  3  × 2 × 2 × 2 × 2 
 36 =  2  ×  3  × 2 × 3 
 18 =  2  ×  3 ×  3 
 Therefore,  the  HCF  of  96,  36  and  18  is 
 the  product  of  the  highest  number  of 
 common  factors  in  the  given  numbers 
 i.e.,  2  ×  3  =  6.  In  other  words,  6  is  the 
 largest  possible  integer,  which  can  divide 
 96,  36  and  18  without  leaving  any 
 remainder. 
 Example:-  Find the H.C.F. of 42 and 70 ? 
 Solution:-  42 = 3 ×  2 × 7 
 70 = 5 ×  2 × 7 
 Hence, H.C.F. of 42 and 70 = 2 × 7 
 = 14. 
 HCF by Division Method 
 Example:-  HCF of 24, 48, 72, and 100. 
 Solution:-  To  start  the  division  method 
 select the smallest two numbers./ 
 HCF of 24 and 48 = 24 
 HCF of 24, 48 and 72 = 24 
 HCF of 24, 48, 72, and 100 = 4. 
 Example:-  HCF of 1785, 1995, 3381. 
 Solution:- 
 HCF of 1785 and 1995 = 105 
 HCF of 1785, 1995 and 3381 = 21 
 NOTE :- 
 (i).  HCF of two prime numbers is 
 always 1. 
 (ii). HCF of co-prime numbers is 
 always 1. 
 Method of finding L.C.M 
 The  Least  Common  Multiple  of  two  or 
 more  numbers  is  the  smallest  number 
 which  is  exactly  divisible  by  all  of  them. 
 In  other  words,  it  is  the  product  of  the 
 highest  powers  of  all  the  prime  factors  of 
 the given numbers. 
 To ?nd the LCM of given numbers: 
 1.  Break  the  given  numbers  into 
 their prime factors. 
 2.  The  LCM  will  be  the  product  of 
 the  highest  power  of  all  the 
 factors  that  occur  in  the  given 
 numbers. 
 Let us take some solved examples. 
 Example:-  Find the LCM of 96, 36 and 18. 
 Solution  : 96 = 2 × 2 × 2 × 2 × 2 × 3 
 =  ×  ; 36 = 2 × 2 × 3 × 3 =  ×  2 
 5 
 3 
 1 
 2 
 2 
 3 
 2 
 18 = 2 × 3 × 3 =  ×  2 
 1 
 3 
 2 
 Therefore,  LCM  of  96,  36  and  18  is  the 
 product  of  the  highest  powers  of  all  the 
 prime factors, i.e. 2 
 5 
 × 3 
 2 
 = 32 × 9 = 288 
 That  is,  288  is  the  smallest  integer  which 
 is  divisible  by  96,  36  and  18  without 
 leaving any remainder. 
 Example:-  Find the LCM of 42 and 70 
 Solution  :- 42 = 3 × 2 × 7 
 70 = 5 × 2 × 7 
 Hence, LCM is 2 × 3 × 5 × 7 = 210. 
 Example:-  LCM of 6, 12, 8 ? 
 Solution  :- 
 LCM =  2     ×     2     ×     3     ×     2 = 24 
 HCF of 6, 12, 18 
 Firstly  ?nd  out  the  factors  of  6,  12,  18 
 and then multiply the common factors. 
 6 =  , 12 =  , 18 =  2     ×     3  2     ×     2     ×     3     2     ×     3     ×     3 
 HCF =  2     ×     3 = 6 
 Try  ?nding  HCF  and  LCM  of  3,  6,  9,  12 
 yourself.  HCF  of  3,  6,  9,  12  can  also  be 
 found  by  Division  method.  It  is  useful 
 when the numbers are bigger. 
 NOTE :- 
 (i).  HCF of A, B and C is the highest 
 divisor which can exactly divide 
 A, B, and C. 
 (ii).  LCM of A, B and C is the lowest 
 dividend which is exactly 
 divisible by A, B, and C. 
 There  is  one  very  important  relationship, 
 given  below,  between  two  numbers  and 
 their  HCF  and  LCM.  Many  problems  have 
 appeared  in  various  competitive  exams 
 based on this relationship. 
 Important Concepts:- 
 (1). 
 LCM × HCF = 1st number × 2nd number 
 Example:-  For numbers 8 and 12, 
 LCM = 24 and HCF = 4 
 Now, LCM  HCF = 24  4 = 96  ×    ×
 also, 8  12 = 96 ×
 (2).  HCF  of  some  numbers  is  always  a 
 factor of LCM of the numbers. 
 (3). 
 LCM of Fraction = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 (4). 
 HCF of Fraction = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 Example:  LCM and HCF of  ,  and 
 1 
 2 
 2 
 3 
 3 
 4 
 Solution:-  LCM = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 =  = 
 ??????     ????     1 , 2 ,       3 
 ??????     ????     2 , 3 , 4 
 6 
 1 
 HCF = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 =  = 
 ??????     ????     1 , 2 ,       3 
 ??????     ????     2 , 3 , 4 
 1 
 12 
 (5)  Co- Prime numbers : 
 If  the  HCF  of  two  numbers  is  1  then  they 
 are called co-prime numbers. 
 (6)  =  ; 
 ?????? 
 ?????? 
 ?????????????? 
 where LCM and HCF are of two numbers 
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Page 2


 Pinnacle  Day:  6th - 7th  HCF and LCM 
 HCF and LCM 
 LCM  (Least  common  multiple)  of  two  or 
 more  given  numbers  is  the  least  number 
 that is exactly divisible by each of them. 
 HCF  (Highest  common  factor)  of  two  or 
 more  numbers  is  the  greatest  number 
 that  divides  each  of  them  exactly.  HCF  is 
 also  known  as  the  ‘Highest  common 
 Divisor’  (HCD)  and  the  Greatest  Common 
 Measure (GCM). 
 The concept of multiples and factors 
 If X , Y , and Z are three natural ?
 numbers and X × Y = Z , then 
 (i).  X and Y are called the factors of 
 Z. 
 (ii). Z is said to be divisible by X and 
 Y. 
 (iii). Z is said to be a multiple of X 
 and Y. 
 Example:  The  set  of  positive  Integers 
 which  are  factors  of  18  is  (1,  2,  3,  6,  9, 
 18). 
 Basic Concepts of  H.C.F. and LCM 
 Method of finding  H.C.F. 
 To ?nd the HCF of the given numbers 
 1.  Break  the  given  numbers  into  their 
 prime factors. 
 2.  The  HCF  will  be  the  product  of  all  the 
 prime  factors  common  to  all  the 
 numbers. 
 Let  us  learn  the  process  of  ?nding  HCF 
 with the help of some solved examples. 
 Example:- 
 Find the HCF of 96, 36 and 18 ? 
 Solution:- 
 96 =  2  ×  3  × 2 × 2 × 2 × 2 
 36 =  2  ×  3  × 2 × 3 
 18 =  2  ×  3 ×  3 
 Therefore,  the  HCF  of  96,  36  and  18  is 
 the  product  of  the  highest  number  of 
 common  factors  in  the  given  numbers 
 i.e.,  2  ×  3  =  6.  In  other  words,  6  is  the 
 largest  possible  integer,  which  can  divide 
 96,  36  and  18  without  leaving  any 
 remainder. 
 Example:-  Find the H.C.F. of 42 and 70 ? 
 Solution:-  42 = 3 ×  2 × 7 
 70 = 5 ×  2 × 7 
 Hence, H.C.F. of 42 and 70 = 2 × 7 
 = 14. 
 HCF by Division Method 
 Example:-  HCF of 24, 48, 72, and 100. 
 Solution:-  To  start  the  division  method 
 select the smallest two numbers./ 
 HCF of 24 and 48 = 24 
 HCF of 24, 48 and 72 = 24 
 HCF of 24, 48, 72, and 100 = 4. 
 Example:-  HCF of 1785, 1995, 3381. 
 Solution:- 
 HCF of 1785 and 1995 = 105 
 HCF of 1785, 1995 and 3381 = 21 
 NOTE :- 
 (i).  HCF of two prime numbers is 
 always 1. 
 (ii). HCF of co-prime numbers is 
 always 1. 
 Method of finding L.C.M 
 The  Least  Common  Multiple  of  two  or 
 more  numbers  is  the  smallest  number 
 which  is  exactly  divisible  by  all  of  them. 
 In  other  words,  it  is  the  product  of  the 
 highest  powers  of  all  the  prime  factors  of 
 the given numbers. 
 To ?nd the LCM of given numbers: 
 1.  Break  the  given  numbers  into 
 their prime factors. 
 2.  The  LCM  will  be  the  product  of 
 the  highest  power  of  all  the 
 factors  that  occur  in  the  given 
 numbers. 
 Let us take some solved examples. 
 Example:-  Find the LCM of 96, 36 and 18. 
 Solution  : 96 = 2 × 2 × 2 × 2 × 2 × 3 
 =  ×  ; 36 = 2 × 2 × 3 × 3 =  ×  2 
 5 
 3 
 1 
 2 
 2 
 3 
 2 
 18 = 2 × 3 × 3 =  ×  2 
 1 
 3 
 2 
 Therefore,  LCM  of  96,  36  and  18  is  the 
 product  of  the  highest  powers  of  all  the 
 prime factors, i.e. 2 
 5 
 × 3 
 2 
 = 32 × 9 = 288 
 That  is,  288  is  the  smallest  integer  which 
 is  divisible  by  96,  36  and  18  without 
 leaving any remainder. 
 Example:-  Find the LCM of 42 and 70 
 Solution  :- 42 = 3 × 2 × 7 
 70 = 5 × 2 × 7 
 Hence, LCM is 2 × 3 × 5 × 7 = 210. 
 Example:-  LCM of 6, 12, 8 ? 
 Solution  :- 
 LCM =  2     ×     2     ×     3     ×     2 = 24 
 HCF of 6, 12, 18 
 Firstly  ?nd  out  the  factors  of  6,  12,  18 
 and then multiply the common factors. 
 6 =  , 12 =  , 18 =  2     ×     3  2     ×     2     ×     3     2     ×     3     ×     3 
 HCF =  2     ×     3 = 6 
 Try  ?nding  HCF  and  LCM  of  3,  6,  9,  12 
 yourself.  HCF  of  3,  6,  9,  12  can  also  be 
 found  by  Division  method.  It  is  useful 
 when the numbers are bigger. 
 NOTE :- 
 (i).  HCF of A, B and C is the highest 
 divisor which can exactly divide 
 A, B, and C. 
 (ii).  LCM of A, B and C is the lowest 
 dividend which is exactly 
 divisible by A, B, and C. 
 There  is  one  very  important  relationship, 
 given  below,  between  two  numbers  and 
 their  HCF  and  LCM.  Many  problems  have 
 appeared  in  various  competitive  exams 
 based on this relationship. 
 Important Concepts:- 
 (1). 
 LCM × HCF = 1st number × 2nd number 
 Example:-  For numbers 8 and 12, 
 LCM = 24 and HCF = 4 
 Now, LCM  HCF = 24  4 = 96  ×    ×
 also, 8  12 = 96 ×
 (2).  HCF  of  some  numbers  is  always  a 
 factor of LCM of the numbers. 
 (3). 
 LCM of Fraction = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 (4). 
 HCF of Fraction = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 Example:  LCM and HCF of  ,  and 
 1 
 2 
 2 
 3 
 3 
 4 
 Solution:-  LCM = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 =  = 
 ??????     ????     1 , 2 ,       3 
 ??????     ????     2 , 3 , 4 
 6 
 1 
 HCF = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 =  = 
 ??????     ????     1 , 2 ,       3 
 ??????     ????     2 , 3 , 4 
 1 
 12 
 (5)  Co- Prime numbers : 
 If  the  HCF  of  two  numbers  is  1  then  they 
 are called co-prime numbers. 
 (6)  =  ; 
 ?????? 
 ?????? 
 ?????????????? 
 where LCM and HCF are of two numbers 
 www.ssccglpinnacle.com                                                 Download Pinnacle Exam Preparation App 27
 Pinnacle  Day:  6th - 7th  HCF and LCM 
 . If we ?nd two co-prime  ?? 
 1 
    ??????     ?? 
 2 
 factors,  , of the Product  ?? 
 1 
    ??????     ?? 
 2 
 as obtained above. 
 (7) 
 Example:- 
 (8). 
 If 1st number =  and 2nd  number =  ?? 
 1 
 ?? 
 2 
 HCF of  = Hx  ?? 
 1 
 HCF of  = Hy  ?? 
 2 
 And HCF of  and  = H  ?? 
 1 
 ?? 
 2 
 So , 
 Difference between  and  = Hx - Hy  ?? 
 1 
 ?? 
 2    
 = H(x - y) 
 Example :- 
 = 24 and  = 36  ?? 
 1 
 ?? 
 2 
 Note  :-  HCF  is  always  either  the 
 difference  of  two  numbers  or  factors  of 
 difference of two numbers. 
 (9).  When  the  second  divisor  is  a  factor 
 of  the  ?rst  divisor,  then  the  second 
 remainder  is  obtained  by  dividing  the  ?rst 
 remainder by the second divisor. 
 Example  :-  When  29  is  divided  by  8,  the 
 remainder  obtained  is  5,  then  what  will 
 be  the  remainder  when  the  same  number 
 is divided by 4 ? 
 Solution:-  Here,  the  second  divisor  that  is 
 4  is  a  factor  of  the  ?rst  divisor  that  is  8. 
 So,  on  dividing  the  ?rst  remainder  that  is 
 5  by  the  second  divisor  that  is  4,  we  get 
 our  second  remainder  which  is  1.  So,  the 
 required answer is 1. 
 Variety Questions 
 Q.1.  The LCM of x² - 8x + 15 and x² - 5x + 6 
 is: 
 SSC CPO 05/10/2023 (2nd Shift) 
 (a) (x + 5)(x + 2)(x + 3) 
 (b) (x - 5)(x - 2)(x - 3) 
 (c) (x + 5)(x - 2)(x - 3) 
 (d) (x - 2)(x - 3) 
 2 
 (x - 5) 
 Q.2.  The greatest possible length that 
 can  be  used  to  measure  exactly  the 
 lengths  of  3  m  15  cm,  5  m,  and  6  m  85 
 cm is: 
 SSC CPO 05/10/2023 (2nd Shift) 
 (a) 11 cm  (b) 7 cm  (c) 9 cm  (d) 5 cm 
 Q.3.  What is the HCF of (  + 1) and (  - 1)  ?? 
 6 
 ?? 
 4 
 SSC CPO 05/10/2023 (1st Shift) 
 (a) (1 +  )  (b) (1 + x)  (c) 1  (d) (1  )  ?? 
 2 
- ?? 
 2 
 Q.4.  The  LCM  of  two  prime  numbers  x 
 and y (x > y) is 533. The value of 4y - x is: 
 SSC CPO 03/10/2023 (3rd Shift) 
 (a) 11  (b) 21  (c) 18  (d) 23 
 Q.5.  What is the HCF of the polynomials 
 (  ³  -  8),  (  ³  -  6  ²  +  12  -  8)  and  (  ³  -  4  ²  +  4  ??  ??  ??  ??  ??  ?? 
 ) ?  ?? 
 SSC MTS 12/09/2023 (3rd Shift) 
 (a) (  - 1)  (b) (  - 2)  (c) (  - 8)  (d) (  - 4)  ??  ??  ??  ?? 
 Q.6.  Find  the  greatest  two  digit  number 
 which  on  dividing  219,  365,  511  leaves 
 the remainders 3, 5, 7, respectively. 
 SSC MTS 01/09/2023 (3rd Shift) 
 (a) 63  (b) 82  (c) 53  (d) 72 
 Q.7.  There  is  a  circular  path  around  a 
 sports  ?eld.  Rahul  takes  15  minutes  to 
 drive  one  round  of  the  ?eld,  while  Anil 
 takes  18  minutes  for  the  same.  Suppose 
 they  both  start  from  the  same  point  and 
 at  the  same  time,  and  go  in  the  same 
 direction.  After  how  many  minutes  will 
 they meet again at the starting point? 
 SSC MTS 11/05/2023 (Afternoon) 
 (a) 120  (b) 100  (c) 80  (d) 90 
 Q.8.  Let  x  =  224  and,  y  =  322.  If  the 
 highest  common  factor  of  23x  and  a  ×  y 
 is  divisible  by  x  and  y,  then  what  can  be 
 the possible value of a? 
 SSC CPO 11/11/2022 (Evening) 
 (a) 16  (b) 8  (c) 12  (d) 4 
 Q.9.  The  highest  common  factor  of  108, 
 72  and  5a  is  a.  What  can  be  the  least 
 common multiple of 108, 72 and a ? 
 SSC CPO 10/11/2022 (Afternoon) 
 (a) 432  (b) 324  (c) 108  (d) 216 
 Q.10.  What  is  the  greatest  positive 
 integer  that  divides  554,  714  and  213 
 leaving  the  remainder  43,  57  and  67, 
 respectively? 
 SSC CPO 10/11/2022 (Afternoon) 
 (a) 95  (b) 71  (c) 83  (d) 73 
 Q.11.  Find the HCF of (  – 1) and  4 
 315 
 (  – 1).  4 
 25 
 SSC MTS 26/07/2022 (Morning) 
 (a) 1    (b) (  – 1)    (c) 1024    (d) 1023  4 
 25 
 Q.12.  120  apples,  240  oranges  and  150 
 pears  are  packed  in  cartons  in  such  a 
 way  that  each  carton  has  the  same 
 number  of  fruits,  each  carton  contains 
 only  one  type  of  fruit  and  fruit  is  left 
 unpacked.  What  is  the  smallest  possible 
 number  of  cartons  needed  for  the 
 purpose ? 
 SSC MTS 08/07/2022 (Evening) 
 (a) 50  (b) 40  (c) 17  (d) 30 
 Q.13.  13,  a,  b,  c  are  four  distinct  numbers 
 and  the  HCF  of  each  pair  of  numbers  (13, 
 a)  :  (13,  b)  :  (13,  c)  is  13,  where  a,  b,  c  are 
 each  less  than  60  and  a  <  b  <  c.  What  is 
 the value of  ? 
 ??    +    ?? 
 ?? 
 SSC CGL 13/04/2021 (Morning) 
 (a) 3.5  (b) 2  (c) 5  (d) 4.5 
 Q.14.  The  sum  of  two  numbers  is  1215 
 and  their  HCF  is  81.  If  the  numbers  lie 
 between  500  and  700,  then  the  sum  of 
 reciprocals of the numbers is 
 SSC CPO 13/12/2019 (Evening) 
 (a)  (b)  (c)  (d) 
 5 
 1512 
 5 
 378 
 5 
 702 
 5 
 1188 
 Q.15.  If  r  is  the  remainder  when  each  of 
 6454,  7306  and  8797  is  divided  by  the 
 greatest number d (d > 1), then (d - r) is: 
 SSC CPO 13/12/2019 (Morning) 
 (a) 126    (b) 64    (c) 137    (d) 149 
 Q.16.  In  ?nding  the  HCF  of  two  numbers 
 by  division  method,  the  quotients  are  1,  8 
 and  2  respectively,  and  the  last  divisor  is 
 105, what is the sum of the numbers? 
 SSC CPO 11/12/2019 (Evening) 
 (a) 3570   (b) 3885   (c) 3780   (d) 3675 
 Q.17.  When  the  smallest  number  x  is 
 divided  by  5,  6,  8,  9  and  12,  it  gives 
 remainder  1  in  each  case.  But  x  is 
 divisible  by  13.  What  will  be  the 
 remainder when x will be divided by 31 
 SSC MTS 20/08/2019 (Afternoon) 
 (a) 1      (b) 5       (c) 3       (d) 0 
 Q.18.  The  Highest  Common  Factor  and 
 Lowest  Common  Multiple  of  two 
 numbers  p  and  q  are  A  and  B 
 respectively.  IF  A  +  B  =  p  +  q,  then  the 
 value of  is :  ?? 
 3 
+ ?? 
 3 
 SSC MTS 09/08/2019 (Evening) 
 (a)  p 
 3 
 (b)  q 
 3 
 (c)  p 
 3 
 +  q 
 3 
 (d)  p 
 3 
 -  q 
 3 
 Q.19.  What  is  the  largest  number  that 
 divides  460,  491  and  553  and  leaves  the 
 remainder 26 in each case ? 
 SSC MTS 06/08/2019 (Afternoon) 
 (a) 27      (b)35      (c) 33      (d) 31 
 Q.20.  A  is  the  smallest  three-digit 
 number  which  when  divided  by  3,  4  and  5 
 gives  remainder  1,  2  and  3  respectively. 
 What is the sum of the digits of A ? 
 SSC MTS 05/08/2019 (Afternoon) 
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Page 3


 Pinnacle  Day:  6th - 7th  HCF and LCM 
 HCF and LCM 
 LCM  (Least  common  multiple)  of  two  or 
 more  given  numbers  is  the  least  number 
 that is exactly divisible by each of them. 
 HCF  (Highest  common  factor)  of  two  or 
 more  numbers  is  the  greatest  number 
 that  divides  each  of  them  exactly.  HCF  is 
 also  known  as  the  ‘Highest  common 
 Divisor’  (HCD)  and  the  Greatest  Common 
 Measure (GCM). 
 The concept of multiples and factors 
 If X , Y , and Z are three natural ?
 numbers and X × Y = Z , then 
 (i).  X and Y are called the factors of 
 Z. 
 (ii). Z is said to be divisible by X and 
 Y. 
 (iii). Z is said to be a multiple of X 
 and Y. 
 Example:  The  set  of  positive  Integers 
 which  are  factors  of  18  is  (1,  2,  3,  6,  9, 
 18). 
 Basic Concepts of  H.C.F. and LCM 
 Method of finding  H.C.F. 
 To ?nd the HCF of the given numbers 
 1.  Break  the  given  numbers  into  their 
 prime factors. 
 2.  The  HCF  will  be  the  product  of  all  the 
 prime  factors  common  to  all  the 
 numbers. 
 Let  us  learn  the  process  of  ?nding  HCF 
 with the help of some solved examples. 
 Example:- 
 Find the HCF of 96, 36 and 18 ? 
 Solution:- 
 96 =  2  ×  3  × 2 × 2 × 2 × 2 
 36 =  2  ×  3  × 2 × 3 
 18 =  2  ×  3 ×  3 
 Therefore,  the  HCF  of  96,  36  and  18  is 
 the  product  of  the  highest  number  of 
 common  factors  in  the  given  numbers 
 i.e.,  2  ×  3  =  6.  In  other  words,  6  is  the 
 largest  possible  integer,  which  can  divide 
 96,  36  and  18  without  leaving  any 
 remainder. 
 Example:-  Find the H.C.F. of 42 and 70 ? 
 Solution:-  42 = 3 ×  2 × 7 
 70 = 5 ×  2 × 7 
 Hence, H.C.F. of 42 and 70 = 2 × 7 
 = 14. 
 HCF by Division Method 
 Example:-  HCF of 24, 48, 72, and 100. 
 Solution:-  To  start  the  division  method 
 select the smallest two numbers./ 
 HCF of 24 and 48 = 24 
 HCF of 24, 48 and 72 = 24 
 HCF of 24, 48, 72, and 100 = 4. 
 Example:-  HCF of 1785, 1995, 3381. 
 Solution:- 
 HCF of 1785 and 1995 = 105 
 HCF of 1785, 1995 and 3381 = 21 
 NOTE :- 
 (i).  HCF of two prime numbers is 
 always 1. 
 (ii). HCF of co-prime numbers is 
 always 1. 
 Method of finding L.C.M 
 The  Least  Common  Multiple  of  two  or 
 more  numbers  is  the  smallest  number 
 which  is  exactly  divisible  by  all  of  them. 
 In  other  words,  it  is  the  product  of  the 
 highest  powers  of  all  the  prime  factors  of 
 the given numbers. 
 To ?nd the LCM of given numbers: 
 1.  Break  the  given  numbers  into 
 their prime factors. 
 2.  The  LCM  will  be  the  product  of 
 the  highest  power  of  all  the 
 factors  that  occur  in  the  given 
 numbers. 
 Let us take some solved examples. 
 Example:-  Find the LCM of 96, 36 and 18. 
 Solution  : 96 = 2 × 2 × 2 × 2 × 2 × 3 
 =  ×  ; 36 = 2 × 2 × 3 × 3 =  ×  2 
 5 
 3 
 1 
 2 
 2 
 3 
 2 
 18 = 2 × 3 × 3 =  ×  2 
 1 
 3 
 2 
 Therefore,  LCM  of  96,  36  and  18  is  the 
 product  of  the  highest  powers  of  all  the 
 prime factors, i.e. 2 
 5 
 × 3 
 2 
 = 32 × 9 = 288 
 That  is,  288  is  the  smallest  integer  which 
 is  divisible  by  96,  36  and  18  without 
 leaving any remainder. 
 Example:-  Find the LCM of 42 and 70 
 Solution  :- 42 = 3 × 2 × 7 
 70 = 5 × 2 × 7 
 Hence, LCM is 2 × 3 × 5 × 7 = 210. 
 Example:-  LCM of 6, 12, 8 ? 
 Solution  :- 
 LCM =  2     ×     2     ×     3     ×     2 = 24 
 HCF of 6, 12, 18 
 Firstly  ?nd  out  the  factors  of  6,  12,  18 
 and then multiply the common factors. 
 6 =  , 12 =  , 18 =  2     ×     3  2     ×     2     ×     3     2     ×     3     ×     3 
 HCF =  2     ×     3 = 6 
 Try  ?nding  HCF  and  LCM  of  3,  6,  9,  12 
 yourself.  HCF  of  3,  6,  9,  12  can  also  be 
 found  by  Division  method.  It  is  useful 
 when the numbers are bigger. 
 NOTE :- 
 (i).  HCF of A, B and C is the highest 
 divisor which can exactly divide 
 A, B, and C. 
 (ii).  LCM of A, B and C is the lowest 
 dividend which is exactly 
 divisible by A, B, and C. 
 There  is  one  very  important  relationship, 
 given  below,  between  two  numbers  and 
 their  HCF  and  LCM.  Many  problems  have 
 appeared  in  various  competitive  exams 
 based on this relationship. 
 Important Concepts:- 
 (1). 
 LCM × HCF = 1st number × 2nd number 
 Example:-  For numbers 8 and 12, 
 LCM = 24 and HCF = 4 
 Now, LCM  HCF = 24  4 = 96  ×    ×
 also, 8  12 = 96 ×
 (2).  HCF  of  some  numbers  is  always  a 
 factor of LCM of the numbers. 
 (3). 
 LCM of Fraction = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 (4). 
 HCF of Fraction = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 Example:  LCM and HCF of  ,  and 
 1 
 2 
 2 
 3 
 3 
 4 
 Solution:-  LCM = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 =  = 
 ??????     ????     1 , 2 ,       3 
 ??????     ????     2 , 3 , 4 
 6 
 1 
 HCF = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 =  = 
 ??????     ????     1 , 2 ,       3 
 ??????     ????     2 , 3 , 4 
 1 
 12 
 (5)  Co- Prime numbers : 
 If  the  HCF  of  two  numbers  is  1  then  they 
 are called co-prime numbers. 
 (6)  =  ; 
 ?????? 
 ?????? 
 ?????????????? 
 where LCM and HCF are of two numbers 
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 Pinnacle  Day:  6th - 7th  HCF and LCM 
 . If we ?nd two co-prime  ?? 
 1 
    ??????     ?? 
 2 
 factors,  , of the Product  ?? 
 1 
    ??????     ?? 
 2 
 as obtained above. 
 (7) 
 Example:- 
 (8). 
 If 1st number =  and 2nd  number =  ?? 
 1 
 ?? 
 2 
 HCF of  = Hx  ?? 
 1 
 HCF of  = Hy  ?? 
 2 
 And HCF of  and  = H  ?? 
 1 
 ?? 
 2 
 So , 
 Difference between  and  = Hx - Hy  ?? 
 1 
 ?? 
 2    
 = H(x - y) 
 Example :- 
 = 24 and  = 36  ?? 
 1 
 ?? 
 2 
 Note  :-  HCF  is  always  either  the 
 difference  of  two  numbers  or  factors  of 
 difference of two numbers. 
 (9).  When  the  second  divisor  is  a  factor 
 of  the  ?rst  divisor,  then  the  second 
 remainder  is  obtained  by  dividing  the  ?rst 
 remainder by the second divisor. 
 Example  :-  When  29  is  divided  by  8,  the 
 remainder  obtained  is  5,  then  what  will 
 be  the  remainder  when  the  same  number 
 is divided by 4 ? 
 Solution:-  Here,  the  second  divisor  that  is 
 4  is  a  factor  of  the  ?rst  divisor  that  is  8. 
 So,  on  dividing  the  ?rst  remainder  that  is 
 5  by  the  second  divisor  that  is  4,  we  get 
 our  second  remainder  which  is  1.  So,  the 
 required answer is 1. 
 Variety Questions 
 Q.1.  The LCM of x² - 8x + 15 and x² - 5x + 6 
 is: 
 SSC CPO 05/10/2023 (2nd Shift) 
 (a) (x + 5)(x + 2)(x + 3) 
 (b) (x - 5)(x - 2)(x - 3) 
 (c) (x + 5)(x - 2)(x - 3) 
 (d) (x - 2)(x - 3) 
 2 
 (x - 5) 
 Q.2.  The greatest possible length that 
 can  be  used  to  measure  exactly  the 
 lengths  of  3  m  15  cm,  5  m,  and  6  m  85 
 cm is: 
 SSC CPO 05/10/2023 (2nd Shift) 
 (a) 11 cm  (b) 7 cm  (c) 9 cm  (d) 5 cm 
 Q.3.  What is the HCF of (  + 1) and (  - 1)  ?? 
 6 
 ?? 
 4 
 SSC CPO 05/10/2023 (1st Shift) 
 (a) (1 +  )  (b) (1 + x)  (c) 1  (d) (1  )  ?? 
 2 
- ?? 
 2 
 Q.4.  The  LCM  of  two  prime  numbers  x 
 and y (x > y) is 533. The value of 4y - x is: 
 SSC CPO 03/10/2023 (3rd Shift) 
 (a) 11  (b) 21  (c) 18  (d) 23 
 Q.5.  What is the HCF of the polynomials 
 (  ³  -  8),  (  ³  -  6  ²  +  12  -  8)  and  (  ³  -  4  ²  +  4  ??  ??  ??  ??  ??  ?? 
 ) ?  ?? 
 SSC MTS 12/09/2023 (3rd Shift) 
 (a) (  - 1)  (b) (  - 2)  (c) (  - 8)  (d) (  - 4)  ??  ??  ??  ?? 
 Q.6.  Find  the  greatest  two  digit  number 
 which  on  dividing  219,  365,  511  leaves 
 the remainders 3, 5, 7, respectively. 
 SSC MTS 01/09/2023 (3rd Shift) 
 (a) 63  (b) 82  (c) 53  (d) 72 
 Q.7.  There  is  a  circular  path  around  a 
 sports  ?eld.  Rahul  takes  15  minutes  to 
 drive  one  round  of  the  ?eld,  while  Anil 
 takes  18  minutes  for  the  same.  Suppose 
 they  both  start  from  the  same  point  and 
 at  the  same  time,  and  go  in  the  same 
 direction.  After  how  many  minutes  will 
 they meet again at the starting point? 
 SSC MTS 11/05/2023 (Afternoon) 
 (a) 120  (b) 100  (c) 80  (d) 90 
 Q.8.  Let  x  =  224  and,  y  =  322.  If  the 
 highest  common  factor  of  23x  and  a  ×  y 
 is  divisible  by  x  and  y,  then  what  can  be 
 the possible value of a? 
 SSC CPO 11/11/2022 (Evening) 
 (a) 16  (b) 8  (c) 12  (d) 4 
 Q.9.  The  highest  common  factor  of  108, 
 72  and  5a  is  a.  What  can  be  the  least 
 common multiple of 108, 72 and a ? 
 SSC CPO 10/11/2022 (Afternoon) 
 (a) 432  (b) 324  (c) 108  (d) 216 
 Q.10.  What  is  the  greatest  positive 
 integer  that  divides  554,  714  and  213 
 leaving  the  remainder  43,  57  and  67, 
 respectively? 
 SSC CPO 10/11/2022 (Afternoon) 
 (a) 95  (b) 71  (c) 83  (d) 73 
 Q.11.  Find the HCF of (  – 1) and  4 
 315 
 (  – 1).  4 
 25 
 SSC MTS 26/07/2022 (Morning) 
 (a) 1    (b) (  – 1)    (c) 1024    (d) 1023  4 
 25 
 Q.12.  120  apples,  240  oranges  and  150 
 pears  are  packed  in  cartons  in  such  a 
 way  that  each  carton  has  the  same 
 number  of  fruits,  each  carton  contains 
 only  one  type  of  fruit  and  fruit  is  left 
 unpacked.  What  is  the  smallest  possible 
 number  of  cartons  needed  for  the 
 purpose ? 
 SSC MTS 08/07/2022 (Evening) 
 (a) 50  (b) 40  (c) 17  (d) 30 
 Q.13.  13,  a,  b,  c  are  four  distinct  numbers 
 and  the  HCF  of  each  pair  of  numbers  (13, 
 a)  :  (13,  b)  :  (13,  c)  is  13,  where  a,  b,  c  are 
 each  less  than  60  and  a  <  b  <  c.  What  is 
 the value of  ? 
 ??    +    ?? 
 ?? 
 SSC CGL 13/04/2021 (Morning) 
 (a) 3.5  (b) 2  (c) 5  (d) 4.5 
 Q.14.  The  sum  of  two  numbers  is  1215 
 and  their  HCF  is  81.  If  the  numbers  lie 
 between  500  and  700,  then  the  sum  of 
 reciprocals of the numbers is 
 SSC CPO 13/12/2019 (Evening) 
 (a)  (b)  (c)  (d) 
 5 
 1512 
 5 
 378 
 5 
 702 
 5 
 1188 
 Q.15.  If  r  is  the  remainder  when  each  of 
 6454,  7306  and  8797  is  divided  by  the 
 greatest number d (d > 1), then (d - r) is: 
 SSC CPO 13/12/2019 (Morning) 
 (a) 126    (b) 64    (c) 137    (d) 149 
 Q.16.  In  ?nding  the  HCF  of  two  numbers 
 by  division  method,  the  quotients  are  1,  8 
 and  2  respectively,  and  the  last  divisor  is 
 105, what is the sum of the numbers? 
 SSC CPO 11/12/2019 (Evening) 
 (a) 3570   (b) 3885   (c) 3780   (d) 3675 
 Q.17.  When  the  smallest  number  x  is 
 divided  by  5,  6,  8,  9  and  12,  it  gives 
 remainder  1  in  each  case.  But  x  is 
 divisible  by  13.  What  will  be  the 
 remainder when x will be divided by 31 
 SSC MTS 20/08/2019 (Afternoon) 
 (a) 1      (b) 5       (c) 3       (d) 0 
 Q.18.  The  Highest  Common  Factor  and 
 Lowest  Common  Multiple  of  two 
 numbers  p  and  q  are  A  and  B 
 respectively.  IF  A  +  B  =  p  +  q,  then  the 
 value of  is :  ?? 
 3 
+ ?? 
 3 
 SSC MTS 09/08/2019 (Evening) 
 (a)  p 
 3 
 (b)  q 
 3 
 (c)  p 
 3 
 +  q 
 3 
 (d)  p 
 3 
 -  q 
 3 
 Q.19.  What  is  the  largest  number  that 
 divides  460,  491  and  553  and  leaves  the 
 remainder 26 in each case ? 
 SSC MTS 06/08/2019 (Afternoon) 
 (a) 27      (b)35      (c) 33      (d) 31 
 Q.20.  A  is  the  smallest  three-digit 
 number  which  when  divided  by  3,  4  and  5 
 gives  remainder  1,  2  and  3  respectively. 
 What is the sum of the digits of A ? 
 SSC MTS 05/08/2019 (Afternoon) 
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 Pinnacle  Day:  6th - 7th  HCF and LCM 
 (a) 11  (b) 10  (c) 6       (d) 8 
 Q.21.  The  product  of  two  numbers  is 
 6760  and  their  HCF  is  13.  How  many 
 such pairs of numbers can be formed? 
 SSC CPO 16/03/2019 (Evening) 
 (a) 2         (b) 3          (c) 1         (d) 4 
 Q.22.  An  oil  merchant  has  3  varieties  of 
 oil  of  volumes  432,  594  and  702 
 respectively.  The  number  of  cans  of 
 equal  size  that  would  be  required  to  ?ll 
 the oil separately is: 
 SSC CPO 16/03/2019 (Afternoon) 
 (a) 13, 15, 17  (b) 8, 11, 13 
 (c) 8, 13, 15  (d) 6, 9, 11 
 Q.23.  Which  of  the  following  statements 
 is true ? 
 SSC CPO 14/03/2019 (Morning) 
 (a) LCM of two natural numbers is 
 divisible by their HCF. 
 (b) HCF + LCM of two numbers = 
 Product of the two numbers. 
 (c) Two prime numbers are co-prime 
 numbers if their LCM is 1. 
 (d) HCF of two numbers is the smallest 
 common divisor of both numbers. 
 Practice Questions 
 SSC CPO 2023 Tier - 1 
 Q.24.  The  largest  number  of  four  digits 
 that is exactly divisible by 17 and 36 is: 
 SSC CPO 03/10/2023 (1st Shift) 
 (a) 8568  (b) 9180  (c) 9792  (d) 7956 
 Q.25.  Two  numbers  are  in  the  ratio  3  :  4. 
 The  product  of  their  HCF  and  LCM  is 
 2700. The sum of the numbers is: 
 SSC CPO 03/10/2023 (1st Shift) 
 (a) 45  (b) 105  (c) 60  (d) 15 
 Q.26.  Find  the  greatest  number  which 
 when  divides  261,  853  and  1221,  leaves  a 
 remainder of 5 in each case. 
 SSC CPO 03/10/2023 (2nd  Shift) 
 (a) 18  (b) 17  (c) 16  (d) 19 
 Q.27.  Find the LCM of  ,  and  . 
 3 
 2 
 81 
 16 
 9 
 8 
 SSC CPO 03/10/2023 (2nd  Shift) 
 (a)  (b)  (c)  (d) 
 111 
 2 
 91 
 2 
 81 
 2 
 101 
 2 
 Q.28.  Find  the  greatest  possible  length 
 (in  metres)  that  can  be  used  to  exactly 
 measure  the  lengths  6  m,  5  m  25  cm  and 
 12 m 50 cm. 
 SSC CPO 03/10/2023 (2nd  Shift) 
 (a) 0.35 m (b) 0.90 m (c) 0.75 m (d) 0.25 m 
 Q.29.  The  least  number  which  should  be 
 added  to  1351  so  that  the  sum  is  exactly 
 divisible by 2, 4, 6 and 8 is: 
 SSC CPO 03/10/2023 (3rd Shift) 
 (a) 13  (b) 11  (c) 15  (d) 17 
 Q.30.  Two  numbers  are  in  the  ratio  of  4: 
 3.  The  product  of  their  HCF  and  LCM  is 
 2700.  The  difference  between  the 
 numbers is: 
 SSC CPO 03/10/2023 (3rd Shift) 
 (a) 25  (b) 30  (c) 15  (d) 105 
 Q.31.  Let  the  HCF  of  m  and  n  be  'a'  and 
 let n = ab, LCM of m and n is given by: 
 SSC CPO 04/10/2023 (1st Shift) 
 (a) ab  (b) am  (c) bm  (d) mn 
 Q.32.  The  LCM  and  HCF  of  two  numbers 
 are  1105  and  5.  If  the  LCM  is  17  times 
 the  ?rst  number,  then  ?nd  the  two 
 numbers. 
 SSC CPO 04/10/2023 (2nd Shift) 
 (a) 55 and 85  (b) 65 and 75 
 (c) 60 and 80  (d) 65 and 85 
 Q.33.  Which  is  the  smallest  natural 
 number  that  is  exactly  divisible  by  each 
 of 96, 108 and 144 ? 
 SSC CPO 04/10/2023 (2nd Shift) 
 (a) 1728   (b) 864   (c) 1296   (d) 2592 
 Q.34.  The HCF of 3888 and 3969 is: 
 SSC CPO 04/10/2023 (2nd Shift) 
 (a) 81  (b) 73  (c) 83  (d) 71 
 Q.35.  A  person  has  three  iron  bars  whose 
 lengths  are  20,  30  and  40  metres, 
 respectively.  He  wants  to  cut  pieces  of 
 the  same  length  from  each  of  the  three 
 bars.  What  is  the  least  number  of  total 
 pieces if he cuts without any wastage ? 
 SSC CPO 04/10/2023 (2nd Shift) 
 (a) 9  (b) 10  (c) 8  (d) 11 
 Q.36.  If  the  HCF  of  45  and  55  is 
 expressible  in  the  form  of  55  ×  5  +  45m, 
 then what is the value of m ? 
 SSC CPO 04/10/2023 (3rd Shift) 
 (a) 5   (b) –6   (c) –5   (d) 6 
 Q.37.  Find  the  least  number  which  when 
 divided  by  4,  9,  12  and  15,  leaves  the 
 remainder 3 in each case. 
 SSC CPO 04/10/2023 (3rd Shift) 
 (a) 193  (b) 183  (c) 360  (d) 180 
 Q.38.  Determine  the  LCM  of  two 
 numbers  if  their  HCF  is  12  and  their  ratio 
 is 13 : 15. 
 SSC CPO 04/10/2023 (3rd Shift) 
 (a) 2450   (b) 1780   (c) 1890   (d) 2340 
 Q.39.  What  is  the  smallest  perfect 
 square  number  which  is  completely 
 divisible by 4, 6, 9, 12 and 15? 
 SSC CPO 04/10/2023 (3rd Shift) 
 (a) 900  (b) 961  (c) 784  (d) 841 
 Q.40.  Which of the following numbers 
 leaves  the  remainder  equal  to  the  highest 
 common  factor  of  6,  8  and  9,  when 
 divided by 6, 8 and 9? 
 SSC CPO 04/10/2023 (3rd Shift) 
 (a) 506  (b) 575  (c) 291  (d) 433 
 Q.41.  Find  the  least  number  which  is 
 exactly divisible by 20, 28, 34, 60 and 75. 
 SSC CPO 05/10/2023 (1st Shift) 
 (a) 34500 (b) 35900 (c) 35700 (d) 36220 
 Q.42.  Three  numbers  are  in  the  ratio  of  5 
 :  7  :  9  and  their  LCM  is  34,650.  Their  HCF 
 is: 
 SSC CPO 05/10/2023 (1st Shift) 
 (a) 110  (b) 315  (c) 99  (d) 55 
 Q.43.  Which  is  the  largest  number  that 
 divides  each  of  1036,  1813  and  3885 
 without leaving any remainder ? 
 SSC CPO 05/10/2023 (1st Shift) 
 (a) 259  (b) 111  (c) 333  (d) 37 
 Q.44.  What  is  the  LCM  of  0.15,  0.18  and 
 0.45 ? 
 SSC CPO 05/10/2023 (2nd Shift) 
 (a) 0.6  (b) 0.9  (c) 0.81  (d) 0.09 
 Q.45.  What  will  be  the  least  number 
 which  when  doubled  will  be  exactly 
 divisible by 12, 14, 16 and 18 ? 
 SSC CPO 05/10/2023 (2nd Shift) 
 (a) 636  (b) 226  (c) 428  (d) 504 
 Q.46.  The  LCM  of  two  numbers  is  ?ve 
 times  their  HCF.  If  the  product  of  the  two 
 numbers  is  20480,  then  ?nd  their  HCF 
 and LCM, respectively. 
 SSC CPO 05/10/2023 (3rd Shift) 
 (a) 64 and 320  (b) 56 and 280 
 (c) 48 and 240  (d) 46 and 230 
 Q.47.  If  the  sum  of  two  numbers  is  60 
 and  their  HCF  and  LCM  are  5  and  60, 
 respectively,  then  the  sum  of  the 
 reciprocals of the numbers will be: 
 SSC CPO 05/10/2023 (3rd Shift) 
 (a)  (b)  (c)  (d) 
 1 
 4 
 1 
 5 
 1 
 11 
 1 
 6 
 Q.48.  Which  of  the  following  is  the 
 greatest  four-digit  number  that  is 
 divisible by 15, 25, 40, and 75? 
 SSC CPO 05/10/2023 (3rd Shift) 
 (a) 9000   (b) 9600   (c) 9500   (d) 9200 
 Q.49.  The  least  number  of  ?ve  digits 
 which  is  exactly  divisible  by  9,  12,  15,  25 
 and 27 is: 
 SSC CPO 05/10/2023 (3rd Shift) 
 (a) 10250 (b) 10800 (c) 10600 (d) 10700 
 SSC MTS 2023 Tier - 1 
 Q.50.  Three  measuring  tapes  are  64  cm 
 72 cm and 96 cm, respectively. What is 
 the least length that can be measured by 
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Page 4


 Pinnacle  Day:  6th - 7th  HCF and LCM 
 HCF and LCM 
 LCM  (Least  common  multiple)  of  two  or 
 more  given  numbers  is  the  least  number 
 that is exactly divisible by each of them. 
 HCF  (Highest  common  factor)  of  two  or 
 more  numbers  is  the  greatest  number 
 that  divides  each  of  them  exactly.  HCF  is 
 also  known  as  the  ‘Highest  common 
 Divisor’  (HCD)  and  the  Greatest  Common 
 Measure (GCM). 
 The concept of multiples and factors 
 If X , Y , and Z are three natural ?
 numbers and X × Y = Z , then 
 (i).  X and Y are called the factors of 
 Z. 
 (ii). Z is said to be divisible by X and 
 Y. 
 (iii). Z is said to be a multiple of X 
 and Y. 
 Example:  The  set  of  positive  Integers 
 which  are  factors  of  18  is  (1,  2,  3,  6,  9, 
 18). 
 Basic Concepts of  H.C.F. and LCM 
 Method of finding  H.C.F. 
 To ?nd the HCF of the given numbers 
 1.  Break  the  given  numbers  into  their 
 prime factors. 
 2.  The  HCF  will  be  the  product  of  all  the 
 prime  factors  common  to  all  the 
 numbers. 
 Let  us  learn  the  process  of  ?nding  HCF 
 with the help of some solved examples. 
 Example:- 
 Find the HCF of 96, 36 and 18 ? 
 Solution:- 
 96 =  2  ×  3  × 2 × 2 × 2 × 2 
 36 =  2  ×  3  × 2 × 3 
 18 =  2  ×  3 ×  3 
 Therefore,  the  HCF  of  96,  36  and  18  is 
 the  product  of  the  highest  number  of 
 common  factors  in  the  given  numbers 
 i.e.,  2  ×  3  =  6.  In  other  words,  6  is  the 
 largest  possible  integer,  which  can  divide 
 96,  36  and  18  without  leaving  any 
 remainder. 
 Example:-  Find the H.C.F. of 42 and 70 ? 
 Solution:-  42 = 3 ×  2 × 7 
 70 = 5 ×  2 × 7 
 Hence, H.C.F. of 42 and 70 = 2 × 7 
 = 14. 
 HCF by Division Method 
 Example:-  HCF of 24, 48, 72, and 100. 
 Solution:-  To  start  the  division  method 
 select the smallest two numbers./ 
 HCF of 24 and 48 = 24 
 HCF of 24, 48 and 72 = 24 
 HCF of 24, 48, 72, and 100 = 4. 
 Example:-  HCF of 1785, 1995, 3381. 
 Solution:- 
 HCF of 1785 and 1995 = 105 
 HCF of 1785, 1995 and 3381 = 21 
 NOTE :- 
 (i).  HCF of two prime numbers is 
 always 1. 
 (ii). HCF of co-prime numbers is 
 always 1. 
 Method of finding L.C.M 
 The  Least  Common  Multiple  of  two  or 
 more  numbers  is  the  smallest  number 
 which  is  exactly  divisible  by  all  of  them. 
 In  other  words,  it  is  the  product  of  the 
 highest  powers  of  all  the  prime  factors  of 
 the given numbers. 
 To ?nd the LCM of given numbers: 
 1.  Break  the  given  numbers  into 
 their prime factors. 
 2.  The  LCM  will  be  the  product  of 
 the  highest  power  of  all  the 
 factors  that  occur  in  the  given 
 numbers. 
 Let us take some solved examples. 
 Example:-  Find the LCM of 96, 36 and 18. 
 Solution  : 96 = 2 × 2 × 2 × 2 × 2 × 3 
 =  ×  ; 36 = 2 × 2 × 3 × 3 =  ×  2 
 5 
 3 
 1 
 2 
 2 
 3 
 2 
 18 = 2 × 3 × 3 =  ×  2 
 1 
 3 
 2 
 Therefore,  LCM  of  96,  36  and  18  is  the 
 product  of  the  highest  powers  of  all  the 
 prime factors, i.e. 2 
 5 
 × 3 
 2 
 = 32 × 9 = 288 
 That  is,  288  is  the  smallest  integer  which 
 is  divisible  by  96,  36  and  18  without 
 leaving any remainder. 
 Example:-  Find the LCM of 42 and 70 
 Solution  :- 42 = 3 × 2 × 7 
 70 = 5 × 2 × 7 
 Hence, LCM is 2 × 3 × 5 × 7 = 210. 
 Example:-  LCM of 6, 12, 8 ? 
 Solution  :- 
 LCM =  2     ×     2     ×     3     ×     2 = 24 
 HCF of 6, 12, 18 
 Firstly  ?nd  out  the  factors  of  6,  12,  18 
 and then multiply the common factors. 
 6 =  , 12 =  , 18 =  2     ×     3  2     ×     2     ×     3     2     ×     3     ×     3 
 HCF =  2     ×     3 = 6 
 Try  ?nding  HCF  and  LCM  of  3,  6,  9,  12 
 yourself.  HCF  of  3,  6,  9,  12  can  also  be 
 found  by  Division  method.  It  is  useful 
 when the numbers are bigger. 
 NOTE :- 
 (i).  HCF of A, B and C is the highest 
 divisor which can exactly divide 
 A, B, and C. 
 (ii).  LCM of A, B and C is the lowest 
 dividend which is exactly 
 divisible by A, B, and C. 
 There  is  one  very  important  relationship, 
 given  below,  between  two  numbers  and 
 their  HCF  and  LCM.  Many  problems  have 
 appeared  in  various  competitive  exams 
 based on this relationship. 
 Important Concepts:- 
 (1). 
 LCM × HCF = 1st number × 2nd number 
 Example:-  For numbers 8 and 12, 
 LCM = 24 and HCF = 4 
 Now, LCM  HCF = 24  4 = 96  ×    ×
 also, 8  12 = 96 ×
 (2).  HCF  of  some  numbers  is  always  a 
 factor of LCM of the numbers. 
 (3). 
 LCM of Fraction = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 (4). 
 HCF of Fraction = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 Example:  LCM and HCF of  ,  and 
 1 
 2 
 2 
 3 
 3 
 4 
 Solution:-  LCM = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 =  = 
 ??????     ????     1 , 2 ,       3 
 ??????     ????     2 , 3 , 4 
 6 
 1 
 HCF = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 =  = 
 ??????     ????     1 , 2 ,       3 
 ??????     ????     2 , 3 , 4 
 1 
 12 
 (5)  Co- Prime numbers : 
 If  the  HCF  of  two  numbers  is  1  then  they 
 are called co-prime numbers. 
 (6)  =  ; 
 ?????? 
 ?????? 
 ?????????????? 
 where LCM and HCF are of two numbers 
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 Pinnacle  Day:  6th - 7th  HCF and LCM 
 . If we ?nd two co-prime  ?? 
 1 
    ??????     ?? 
 2 
 factors,  , of the Product  ?? 
 1 
    ??????     ?? 
 2 
 as obtained above. 
 (7) 
 Example:- 
 (8). 
 If 1st number =  and 2nd  number =  ?? 
 1 
 ?? 
 2 
 HCF of  = Hx  ?? 
 1 
 HCF of  = Hy  ?? 
 2 
 And HCF of  and  = H  ?? 
 1 
 ?? 
 2 
 So , 
 Difference between  and  = Hx - Hy  ?? 
 1 
 ?? 
 2    
 = H(x - y) 
 Example :- 
 = 24 and  = 36  ?? 
 1 
 ?? 
 2 
 Note  :-  HCF  is  always  either  the 
 difference  of  two  numbers  or  factors  of 
 difference of two numbers. 
 (9).  When  the  second  divisor  is  a  factor 
 of  the  ?rst  divisor,  then  the  second 
 remainder  is  obtained  by  dividing  the  ?rst 
 remainder by the second divisor. 
 Example  :-  When  29  is  divided  by  8,  the 
 remainder  obtained  is  5,  then  what  will 
 be  the  remainder  when  the  same  number 
 is divided by 4 ? 
 Solution:-  Here,  the  second  divisor  that  is 
 4  is  a  factor  of  the  ?rst  divisor  that  is  8. 
 So,  on  dividing  the  ?rst  remainder  that  is 
 5  by  the  second  divisor  that  is  4,  we  get 
 our  second  remainder  which  is  1.  So,  the 
 required answer is 1. 
 Variety Questions 
 Q.1.  The LCM of x² - 8x + 15 and x² - 5x + 6 
 is: 
 SSC CPO 05/10/2023 (2nd Shift) 
 (a) (x + 5)(x + 2)(x + 3) 
 (b) (x - 5)(x - 2)(x - 3) 
 (c) (x + 5)(x - 2)(x - 3) 
 (d) (x - 2)(x - 3) 
 2 
 (x - 5) 
 Q.2.  The greatest possible length that 
 can  be  used  to  measure  exactly  the 
 lengths  of  3  m  15  cm,  5  m,  and  6  m  85 
 cm is: 
 SSC CPO 05/10/2023 (2nd Shift) 
 (a) 11 cm  (b) 7 cm  (c) 9 cm  (d) 5 cm 
 Q.3.  What is the HCF of (  + 1) and (  - 1)  ?? 
 6 
 ?? 
 4 
 SSC CPO 05/10/2023 (1st Shift) 
 (a) (1 +  )  (b) (1 + x)  (c) 1  (d) (1  )  ?? 
 2 
- ?? 
 2 
 Q.4.  The  LCM  of  two  prime  numbers  x 
 and y (x > y) is 533. The value of 4y - x is: 
 SSC CPO 03/10/2023 (3rd Shift) 
 (a) 11  (b) 21  (c) 18  (d) 23 
 Q.5.  What is the HCF of the polynomials 
 (  ³  -  8),  (  ³  -  6  ²  +  12  -  8)  and  (  ³  -  4  ²  +  4  ??  ??  ??  ??  ??  ?? 
 ) ?  ?? 
 SSC MTS 12/09/2023 (3rd Shift) 
 (a) (  - 1)  (b) (  - 2)  (c) (  - 8)  (d) (  - 4)  ??  ??  ??  ?? 
 Q.6.  Find  the  greatest  two  digit  number 
 which  on  dividing  219,  365,  511  leaves 
 the remainders 3, 5, 7, respectively. 
 SSC MTS 01/09/2023 (3rd Shift) 
 (a) 63  (b) 82  (c) 53  (d) 72 
 Q.7.  There  is  a  circular  path  around  a 
 sports  ?eld.  Rahul  takes  15  minutes  to 
 drive  one  round  of  the  ?eld,  while  Anil 
 takes  18  minutes  for  the  same.  Suppose 
 they  both  start  from  the  same  point  and 
 at  the  same  time,  and  go  in  the  same 
 direction.  After  how  many  minutes  will 
 they meet again at the starting point? 
 SSC MTS 11/05/2023 (Afternoon) 
 (a) 120  (b) 100  (c) 80  (d) 90 
 Q.8.  Let  x  =  224  and,  y  =  322.  If  the 
 highest  common  factor  of  23x  and  a  ×  y 
 is  divisible  by  x  and  y,  then  what  can  be 
 the possible value of a? 
 SSC CPO 11/11/2022 (Evening) 
 (a) 16  (b) 8  (c) 12  (d) 4 
 Q.9.  The  highest  common  factor  of  108, 
 72  and  5a  is  a.  What  can  be  the  least 
 common multiple of 108, 72 and a ? 
 SSC CPO 10/11/2022 (Afternoon) 
 (a) 432  (b) 324  (c) 108  (d) 216 
 Q.10.  What  is  the  greatest  positive 
 integer  that  divides  554,  714  and  213 
 leaving  the  remainder  43,  57  and  67, 
 respectively? 
 SSC CPO 10/11/2022 (Afternoon) 
 (a) 95  (b) 71  (c) 83  (d) 73 
 Q.11.  Find the HCF of (  – 1) and  4 
 315 
 (  – 1).  4 
 25 
 SSC MTS 26/07/2022 (Morning) 
 (a) 1    (b) (  – 1)    (c) 1024    (d) 1023  4 
 25 
 Q.12.  120  apples,  240  oranges  and  150 
 pears  are  packed  in  cartons  in  such  a 
 way  that  each  carton  has  the  same 
 number  of  fruits,  each  carton  contains 
 only  one  type  of  fruit  and  fruit  is  left 
 unpacked.  What  is  the  smallest  possible 
 number  of  cartons  needed  for  the 
 purpose ? 
 SSC MTS 08/07/2022 (Evening) 
 (a) 50  (b) 40  (c) 17  (d) 30 
 Q.13.  13,  a,  b,  c  are  four  distinct  numbers 
 and  the  HCF  of  each  pair  of  numbers  (13, 
 a)  :  (13,  b)  :  (13,  c)  is  13,  where  a,  b,  c  are 
 each  less  than  60  and  a  <  b  <  c.  What  is 
 the value of  ? 
 ??    +    ?? 
 ?? 
 SSC CGL 13/04/2021 (Morning) 
 (a) 3.5  (b) 2  (c) 5  (d) 4.5 
 Q.14.  The  sum  of  two  numbers  is  1215 
 and  their  HCF  is  81.  If  the  numbers  lie 
 between  500  and  700,  then  the  sum  of 
 reciprocals of the numbers is 
 SSC CPO 13/12/2019 (Evening) 
 (a)  (b)  (c)  (d) 
 5 
 1512 
 5 
 378 
 5 
 702 
 5 
 1188 
 Q.15.  If  r  is  the  remainder  when  each  of 
 6454,  7306  and  8797  is  divided  by  the 
 greatest number d (d > 1), then (d - r) is: 
 SSC CPO 13/12/2019 (Morning) 
 (a) 126    (b) 64    (c) 137    (d) 149 
 Q.16.  In  ?nding  the  HCF  of  two  numbers 
 by  division  method,  the  quotients  are  1,  8 
 and  2  respectively,  and  the  last  divisor  is 
 105, what is the sum of the numbers? 
 SSC CPO 11/12/2019 (Evening) 
 (a) 3570   (b) 3885   (c) 3780   (d) 3675 
 Q.17.  When  the  smallest  number  x  is 
 divided  by  5,  6,  8,  9  and  12,  it  gives 
 remainder  1  in  each  case.  But  x  is 
 divisible  by  13.  What  will  be  the 
 remainder when x will be divided by 31 
 SSC MTS 20/08/2019 (Afternoon) 
 (a) 1      (b) 5       (c) 3       (d) 0 
 Q.18.  The  Highest  Common  Factor  and 
 Lowest  Common  Multiple  of  two 
 numbers  p  and  q  are  A  and  B 
 respectively.  IF  A  +  B  =  p  +  q,  then  the 
 value of  is :  ?? 
 3 
+ ?? 
 3 
 SSC MTS 09/08/2019 (Evening) 
 (a)  p 
 3 
 (b)  q 
 3 
 (c)  p 
 3 
 +  q 
 3 
 (d)  p 
 3 
 -  q 
 3 
 Q.19.  What  is  the  largest  number  that 
 divides  460,  491  and  553  and  leaves  the 
 remainder 26 in each case ? 
 SSC MTS 06/08/2019 (Afternoon) 
 (a) 27      (b)35      (c) 33      (d) 31 
 Q.20.  A  is  the  smallest  three-digit 
 number  which  when  divided  by  3,  4  and  5 
 gives  remainder  1,  2  and  3  respectively. 
 What is the sum of the digits of A ? 
 SSC MTS 05/08/2019 (Afternoon) 
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 Pinnacle  Day:  6th - 7th  HCF and LCM 
 (a) 11  (b) 10  (c) 6       (d) 8 
 Q.21.  The  product  of  two  numbers  is 
 6760  and  their  HCF  is  13.  How  many 
 such pairs of numbers can be formed? 
 SSC CPO 16/03/2019 (Evening) 
 (a) 2         (b) 3          (c) 1         (d) 4 
 Q.22.  An  oil  merchant  has  3  varieties  of 
 oil  of  volumes  432,  594  and  702 
 respectively.  The  number  of  cans  of 
 equal  size  that  would  be  required  to  ?ll 
 the oil separately is: 
 SSC CPO 16/03/2019 (Afternoon) 
 (a) 13, 15, 17  (b) 8, 11, 13 
 (c) 8, 13, 15  (d) 6, 9, 11 
 Q.23.  Which  of  the  following  statements 
 is true ? 
 SSC CPO 14/03/2019 (Morning) 
 (a) LCM of two natural numbers is 
 divisible by their HCF. 
 (b) HCF + LCM of two numbers = 
 Product of the two numbers. 
 (c) Two prime numbers are co-prime 
 numbers if their LCM is 1. 
 (d) HCF of two numbers is the smallest 
 common divisor of both numbers. 
 Practice Questions 
 SSC CPO 2023 Tier - 1 
 Q.24.  The  largest  number  of  four  digits 
 that is exactly divisible by 17 and 36 is: 
 SSC CPO 03/10/2023 (1st Shift) 
 (a) 8568  (b) 9180  (c) 9792  (d) 7956 
 Q.25.  Two  numbers  are  in  the  ratio  3  :  4. 
 The  product  of  their  HCF  and  LCM  is 
 2700. The sum of the numbers is: 
 SSC CPO 03/10/2023 (1st Shift) 
 (a) 45  (b) 105  (c) 60  (d) 15 
 Q.26.  Find  the  greatest  number  which 
 when  divides  261,  853  and  1221,  leaves  a 
 remainder of 5 in each case. 
 SSC CPO 03/10/2023 (2nd  Shift) 
 (a) 18  (b) 17  (c) 16  (d) 19 
 Q.27.  Find the LCM of  ,  and  . 
 3 
 2 
 81 
 16 
 9 
 8 
 SSC CPO 03/10/2023 (2nd  Shift) 
 (a)  (b)  (c)  (d) 
 111 
 2 
 91 
 2 
 81 
 2 
 101 
 2 
 Q.28.  Find  the  greatest  possible  length 
 (in  metres)  that  can  be  used  to  exactly 
 measure  the  lengths  6  m,  5  m  25  cm  and 
 12 m 50 cm. 
 SSC CPO 03/10/2023 (2nd  Shift) 
 (a) 0.35 m (b) 0.90 m (c) 0.75 m (d) 0.25 m 
 Q.29.  The  least  number  which  should  be 
 added  to  1351  so  that  the  sum  is  exactly 
 divisible by 2, 4, 6 and 8 is: 
 SSC CPO 03/10/2023 (3rd Shift) 
 (a) 13  (b) 11  (c) 15  (d) 17 
 Q.30.  Two  numbers  are  in  the  ratio  of  4: 
 3.  The  product  of  their  HCF  and  LCM  is 
 2700.  The  difference  between  the 
 numbers is: 
 SSC CPO 03/10/2023 (3rd Shift) 
 (a) 25  (b) 30  (c) 15  (d) 105 
 Q.31.  Let  the  HCF  of  m  and  n  be  'a'  and 
 let n = ab, LCM of m and n is given by: 
 SSC CPO 04/10/2023 (1st Shift) 
 (a) ab  (b) am  (c) bm  (d) mn 
 Q.32.  The  LCM  and  HCF  of  two  numbers 
 are  1105  and  5.  If  the  LCM  is  17  times 
 the  ?rst  number,  then  ?nd  the  two 
 numbers. 
 SSC CPO 04/10/2023 (2nd Shift) 
 (a) 55 and 85  (b) 65 and 75 
 (c) 60 and 80  (d) 65 and 85 
 Q.33.  Which  is  the  smallest  natural 
 number  that  is  exactly  divisible  by  each 
 of 96, 108 and 144 ? 
 SSC CPO 04/10/2023 (2nd Shift) 
 (a) 1728   (b) 864   (c) 1296   (d) 2592 
 Q.34.  The HCF of 3888 and 3969 is: 
 SSC CPO 04/10/2023 (2nd Shift) 
 (a) 81  (b) 73  (c) 83  (d) 71 
 Q.35.  A  person  has  three  iron  bars  whose 
 lengths  are  20,  30  and  40  metres, 
 respectively.  He  wants  to  cut  pieces  of 
 the  same  length  from  each  of  the  three 
 bars.  What  is  the  least  number  of  total 
 pieces if he cuts without any wastage ? 
 SSC CPO 04/10/2023 (2nd Shift) 
 (a) 9  (b) 10  (c) 8  (d) 11 
 Q.36.  If  the  HCF  of  45  and  55  is 
 expressible  in  the  form  of  55  ×  5  +  45m, 
 then what is the value of m ? 
 SSC CPO 04/10/2023 (3rd Shift) 
 (a) 5   (b) –6   (c) –5   (d) 6 
 Q.37.  Find  the  least  number  which  when 
 divided  by  4,  9,  12  and  15,  leaves  the 
 remainder 3 in each case. 
 SSC CPO 04/10/2023 (3rd Shift) 
 (a) 193  (b) 183  (c) 360  (d) 180 
 Q.38.  Determine  the  LCM  of  two 
 numbers  if  their  HCF  is  12  and  their  ratio 
 is 13 : 15. 
 SSC CPO 04/10/2023 (3rd Shift) 
 (a) 2450   (b) 1780   (c) 1890   (d) 2340 
 Q.39.  What  is  the  smallest  perfect 
 square  number  which  is  completely 
 divisible by 4, 6, 9, 12 and 15? 
 SSC CPO 04/10/2023 (3rd Shift) 
 (a) 900  (b) 961  (c) 784  (d) 841 
 Q.40.  Which of the following numbers 
 leaves  the  remainder  equal  to  the  highest 
 common  factor  of  6,  8  and  9,  when 
 divided by 6, 8 and 9? 
 SSC CPO 04/10/2023 (3rd Shift) 
 (a) 506  (b) 575  (c) 291  (d) 433 
 Q.41.  Find  the  least  number  which  is 
 exactly divisible by 20, 28, 34, 60 and 75. 
 SSC CPO 05/10/2023 (1st Shift) 
 (a) 34500 (b) 35900 (c) 35700 (d) 36220 
 Q.42.  Three  numbers  are  in  the  ratio  of  5 
 :  7  :  9  and  their  LCM  is  34,650.  Their  HCF 
 is: 
 SSC CPO 05/10/2023 (1st Shift) 
 (a) 110  (b) 315  (c) 99  (d) 55 
 Q.43.  Which  is  the  largest  number  that 
 divides  each  of  1036,  1813  and  3885 
 without leaving any remainder ? 
 SSC CPO 05/10/2023 (1st Shift) 
 (a) 259  (b) 111  (c) 333  (d) 37 
 Q.44.  What  is  the  LCM  of  0.15,  0.18  and 
 0.45 ? 
 SSC CPO 05/10/2023 (2nd Shift) 
 (a) 0.6  (b) 0.9  (c) 0.81  (d) 0.09 
 Q.45.  What  will  be  the  least  number 
 which  when  doubled  will  be  exactly 
 divisible by 12, 14, 16 and 18 ? 
 SSC CPO 05/10/2023 (2nd Shift) 
 (a) 636  (b) 226  (c) 428  (d) 504 
 Q.46.  The  LCM  of  two  numbers  is  ?ve 
 times  their  HCF.  If  the  product  of  the  two 
 numbers  is  20480,  then  ?nd  their  HCF 
 and LCM, respectively. 
 SSC CPO 05/10/2023 (3rd Shift) 
 (a) 64 and 320  (b) 56 and 280 
 (c) 48 and 240  (d) 46 and 230 
 Q.47.  If  the  sum  of  two  numbers  is  60 
 and  their  HCF  and  LCM  are  5  and  60, 
 respectively,  then  the  sum  of  the 
 reciprocals of the numbers will be: 
 SSC CPO 05/10/2023 (3rd Shift) 
 (a)  (b)  (c)  (d) 
 1 
 4 
 1 
 5 
 1 
 11 
 1 
 6 
 Q.48.  Which  of  the  following  is  the 
 greatest  four-digit  number  that  is 
 divisible by 15, 25, 40, and 75? 
 SSC CPO 05/10/2023 (3rd Shift) 
 (a) 9000   (b) 9600   (c) 9500   (d) 9200 
 Q.49.  The  least  number  of  ?ve  digits 
 which  is  exactly  divisible  by  9,  12,  15,  25 
 and 27 is: 
 SSC CPO 05/10/2023 (3rd Shift) 
 (a) 10250 (b) 10800 (c) 10600 (d) 10700 
 SSC MTS 2023 Tier - 1 
 Q.50.  Three  measuring  tapes  are  64  cm 
 72 cm and 96 cm, respectively. What is 
 the least length that can be measured by 
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 Pinnacle  Day:  6th - 7th  HCF and LCM 
 any of the tapes exactly (in cm)? 
 SSC MTS 04/09/2023 (1st Shift) 
 (a) 575  (b) 570  (c) 576  (d) 525 
 Q.51.  What  is  the  largest  number  that 
 divides  627,  15630  and  3128  and  leaves 
 remainders of 2, 5 and 3, respectively? 
 SSC MTS 04/09/2023 (3rd Shift) 
 (a) 775  (b) 650  (c) 625  (d) 1225 
 Q.52.  The  HCF  of  three  numbers  is  57.  If 
 they  are  in  the  ratio  of  4  :  5  :  6,  then  ?nd 
 the numbers. 
 SSC MTS 05/09/2023 (2nd Shift) 
 (a) 228, 285, 342            (b) 236, 295, 354 
 (c) 240, 300, 360            (d) 232, 290, 348 
 Q.53.  Three  numbers  are  in  the  ratio  3  :  5 
 : 7 If their LCM is 2625, ?nd their HCF. 
 SSC MTS 05/09/2023 (3rd Shift) 
 (a) 100  (b) 125  (c) 50   (d) 25 
 Q.54.  Two  tankers  contain  850  litres  and 
 680  litres  of  oil.  Find  the  maximum 
 capacity  of  a  container  which  can 
 measure  the  oil  of  both  tankers  when 
 used, an exact number of times. 
 SSC MTS 06/09/2023 (2nd Shift) 
 (a) 425 litres  (b) 680 litres 
 (c) 340 litres  (d) 170 litres 
 Q.55.  The  largest  three-digit  number 
 which  gives  the  same  remainder  2  when 
 divided by 3, 5 and 9 is ________. 
 SSC MTS 08/09/2023 (1st Shift) 
 (a) 980  (b) 992  (c) 995  (d) 990 
 Q.56.  The LCM of  ,  ,  ,  is: 
 1    
 6    
 5    
 27    
 4    
 15       
 8    
 3       
 SSC MTS 08/09/2023 (3rd Shift) 
 (a)  (b)  (c)  (d) 
 40       
 3    
    3    
 28    
 5    
 28    
 40    
 5    
 Q.57.  Sanjay  wants  to  exactly  measure 
 the  lengths  7000  mm,  3850  mm  and 
 12950  mm  using  a  single  measuring 
 tape.  What  will  be  the  greatest  possible 
 length (in cm) of the measuring tape? 
 SSC MTS 11/09/2023 (2nd Shift) 
 (a) 40  (b) 45  (c) 35  (d) 30 
 Q.58.  Radha,  Pratima  and  Reena  begin  to 
 jog  around  a  circular  path  and  they 
 complete  their  revolutions  in  50  seconds, 
 75  seconds  and  100  seconds, 
 respectively.  After  how  much  time  (in 
 minutes)  will  they  meet  together  at  the 
 starting point for the ?rst time? 
 SSC MTS 11/09/2023 (3rd Shift) 
 (a) 6  (b) 5  (c) 4  (d) 3 
 Q.59.  The  HCF  of  two  numbers  is  12. 
 Which  of  the  following  can  never  be  their 
 LCM ? 
 SSC MTS 12/09/2023 (1st Shift) 
 (a) 24  (b) 74  (c) 48  (d) 60 
 Q.60.  The  product  of  two  numbers  is 
 4107.  If  the  HCF  of  these  numbers  is  37, 
 then the greater number is: 
 SSC MTS 12/09/2023 (2nd Shift) 
 (a) 111  (b) 74  (c) 185  (d) 37 
 Q.61.  Two numbers are in the ratio of 
 13  :  15.  If  their  HCF  is  3,  then  what  is  the 
 difference between these two numbers ? 
 SSC MTS 13/09/2023 (1st Shift) 
 (a) 4  (b) 2  (c) 8  (d) 6 
 Q.62.  The  LCM  of  the  two  numbers  is 
 1440  and  their  HCF  is  32.  If  the  ?rst 
 number  is  288,  then  ?nd  the  second 
 number. 
 SSC MTS 13/09/2023 (2nd Shift) 
 (a) 150  (b) 145  (c) 180  (d) 160 
 Q.63.  What  is  the  greatest  three-digit 
 number  which  when  divided  by  4,  8  and 
 9, leaves no remainder? 
 SSC MTS 13/09/2023 (3rd Shift) 
 (a) 924  (b) 963  (c) 932  (d) 936 
 Q.64.  Find  the  smallest  three  digit 
 number  which  when  added  to  5  is  exactly 
 divisible by 12, 14 and 18. 
 SSC MTS 14/09/2023 (2nd Shift) 
 (a) 240  (b) 225  (c) 245  (d) 247 
 Q.65.  The  ratio  of  two  numbers  is  3  :  4.  If 
 the  sum  of  these  two  numbers  is  70,  then 
 what is their LCM ? 
 SSC MTS 14/09/2023 (3rd Shift) 
 (a) 120  (b) 96  (c) 108  (d) 84 
 SSC CGL 2023 Tier - 1 
 Q.66.  Find  the  least  number  divisible  by 
 2,  3,  5,  6,  9  and  18,  which  is  a  perfect 
 square. 
 SSC CGL 24/07/2023 (2nd shift) 
 (a) 900  (b) 400  (c) 144  (d) 3600 
 SSC Selection Post (Phase - XI) 
 Q.67.  The  smallest  six-digit  number 
 which is divisible by 12, 16, 24, 28 is: 
 Matriculation Level 30/06/2023 (Shift - 3) 
 (a) 100128  (b) 100190 
 (c) 100180  (d) 100160 
 SSC CHSL 2022 Tier - 2 
 Q.68.  The  HCF  of  two  numbers  is 
 one-twentieth  of  their  LCM.  If  one  of  the 
 numbers  is  96  and  the  difference  of  the 
 LCM  and  the  HCF  is  456,  then  what  is  the 
 other number ? 
 SSC CHSL Tier II (26/06/2023) 
 (a) 48  (b) 120  (c) 144  (d) 72 
 SSC MTS 2022 Tier - 1 
 Q.69.  What is the HCF of two prime 
 numbers X and Y ? 
 SSC MTS 02/05/2023 (Morning) 
 (a) 1  (b) 2  (c) Y  (d) X 
 Q.70.  Two  numbers  are  in  the  ratio  11  :  6. 
 If  their  HCF  is  4,  ?nd  the  smallest 
 number. 
 SSC MTS 02/05/2023 (Afternoon) 
 (a) 30    (b) 18    (c) 24    (d) 12 
 Q.71.  Three  metal  rods  of  length  77  cm, 
 110  cm  and  121  cm  are  to  be  cut  into 
 parts  of  equal  length.  Each  part  must  be 
 as  long  as  possible.  What  is  the  maximum 
 number of pieces that can be cut? 
 SSC MTS 03/05/2023 (Morning) 
 (a) 18  (b) 28  (c) 11  (d) 21 
 Q.72.  What  is  that  least  number  that 
 should  be  added  to  478  so  that  the 
 number  obtained  becomes  exactly 
 divisible by 5, 6 and 12 ? 
 SSC MTS 04/05/2023 (Morning) 
 (a) 62  (b) 12  (c) 2  (d) 52 
 Q.73.  The  product  of  two  co-prime 
 numbers  is  483.  Find  the  Least  Common 
 Multiple of both numbers. 
 SSC MTS 08/05/2023 (Afternoon) 
 (a) 483  (b) 21  (c) 1  (d) 23 
 Q.74.  What  is  that  greatest  four-digit 
 number  which  when  divided  by  3  and  4 
 leaves remainder 2 in each case? 
 SSC MTS 09/05/2023 (Morning) 
 (a) 9994  (b) 9996  (c) 9998  (d) 9995 
 Q.75.  What  is  that  least  perfect  square 
 which  is  exactly  divisible  by  each  of  14, 
 84 and 28 ? 
 SSC MTS 10/05/2023 (Afternoon) 
 (a) 7056    (b) 3528     (c) 1764     (d) 441 
 Q.76.  Find  the  LCM  of  reciprocals  of  22 
 and 16. 
 SSC MTS 11/05/2023 (Evening) 
 (a)  (b)  (c)  (d) 
 1 
 2 
 1 
 3 
 1 
 6 
 1 
 4 
 Q.77.  The  greatest  number  which  when 
 divides  456  and  553  leaves  the 
 remainder as 6 and 3 respectively is: 
 SSC MTS 12/05/2023 (Evening) 
 (a) 5  (b) 50  (c) 10  (d) 30 
 Q.78.  The  least  number  which  when 
 divided  by  14,  18  and  36  and  leaves  1  as 
 remainder in each case is: 
 SSC MTS 16/05/2023 (Morning) 
 (a) 250  (b) 252  (c) 253  (d) 251 
 Q.79.  Three  numbers  are  in  the  ratio  2  :  3 
 :  5  and  their  LCM  is  60.  What  is  the  HCF 
 of the numbers? 
 SSC MTS 16/05/2023 (Evening) 
 (a) 2  (b) 4  (c) 10  (d) 6 
 Q.80.  Five bells commence tolling 
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Page 5


 Pinnacle  Day:  6th - 7th  HCF and LCM 
 HCF and LCM 
 LCM  (Least  common  multiple)  of  two  or 
 more  given  numbers  is  the  least  number 
 that is exactly divisible by each of them. 
 HCF  (Highest  common  factor)  of  two  or 
 more  numbers  is  the  greatest  number 
 that  divides  each  of  them  exactly.  HCF  is 
 also  known  as  the  ‘Highest  common 
 Divisor’  (HCD)  and  the  Greatest  Common 
 Measure (GCM). 
 The concept of multiples and factors 
 If X , Y , and Z are three natural ?
 numbers and X × Y = Z , then 
 (i).  X and Y are called the factors of 
 Z. 
 (ii). Z is said to be divisible by X and 
 Y. 
 (iii). Z is said to be a multiple of X 
 and Y. 
 Example:  The  set  of  positive  Integers 
 which  are  factors  of  18  is  (1,  2,  3,  6,  9, 
 18). 
 Basic Concepts of  H.C.F. and LCM 
 Method of finding  H.C.F. 
 To ?nd the HCF of the given numbers 
 1.  Break  the  given  numbers  into  their 
 prime factors. 
 2.  The  HCF  will  be  the  product  of  all  the 
 prime  factors  common  to  all  the 
 numbers. 
 Let  us  learn  the  process  of  ?nding  HCF 
 with the help of some solved examples. 
 Example:- 
 Find the HCF of 96, 36 and 18 ? 
 Solution:- 
 96 =  2  ×  3  × 2 × 2 × 2 × 2 
 36 =  2  ×  3  × 2 × 3 
 18 =  2  ×  3 ×  3 
 Therefore,  the  HCF  of  96,  36  and  18  is 
 the  product  of  the  highest  number  of 
 common  factors  in  the  given  numbers 
 i.e.,  2  ×  3  =  6.  In  other  words,  6  is  the 
 largest  possible  integer,  which  can  divide 
 96,  36  and  18  without  leaving  any 
 remainder. 
 Example:-  Find the H.C.F. of 42 and 70 ? 
 Solution:-  42 = 3 ×  2 × 7 
 70 = 5 ×  2 × 7 
 Hence, H.C.F. of 42 and 70 = 2 × 7 
 = 14. 
 HCF by Division Method 
 Example:-  HCF of 24, 48, 72, and 100. 
 Solution:-  To  start  the  division  method 
 select the smallest two numbers./ 
 HCF of 24 and 48 = 24 
 HCF of 24, 48 and 72 = 24 
 HCF of 24, 48, 72, and 100 = 4. 
 Example:-  HCF of 1785, 1995, 3381. 
 Solution:- 
 HCF of 1785 and 1995 = 105 
 HCF of 1785, 1995 and 3381 = 21 
 NOTE :- 
 (i).  HCF of two prime numbers is 
 always 1. 
 (ii). HCF of co-prime numbers is 
 always 1. 
 Method of finding L.C.M 
 The  Least  Common  Multiple  of  two  or 
 more  numbers  is  the  smallest  number 
 which  is  exactly  divisible  by  all  of  them. 
 In  other  words,  it  is  the  product  of  the 
 highest  powers  of  all  the  prime  factors  of 
 the given numbers. 
 To ?nd the LCM of given numbers: 
 1.  Break  the  given  numbers  into 
 their prime factors. 
 2.  The  LCM  will  be  the  product  of 
 the  highest  power  of  all  the 
 factors  that  occur  in  the  given 
 numbers. 
 Let us take some solved examples. 
 Example:-  Find the LCM of 96, 36 and 18. 
 Solution  : 96 = 2 × 2 × 2 × 2 × 2 × 3 
 =  ×  ; 36 = 2 × 2 × 3 × 3 =  ×  2 
 5 
 3 
 1 
 2 
 2 
 3 
 2 
 18 = 2 × 3 × 3 =  ×  2 
 1 
 3 
 2 
 Therefore,  LCM  of  96,  36  and  18  is  the 
 product  of  the  highest  powers  of  all  the 
 prime factors, i.e. 2 
 5 
 × 3 
 2 
 = 32 × 9 = 288 
 That  is,  288  is  the  smallest  integer  which 
 is  divisible  by  96,  36  and  18  without 
 leaving any remainder. 
 Example:-  Find the LCM of 42 and 70 
 Solution  :- 42 = 3 × 2 × 7 
 70 = 5 × 2 × 7 
 Hence, LCM is 2 × 3 × 5 × 7 = 210. 
 Example:-  LCM of 6, 12, 8 ? 
 Solution  :- 
 LCM =  2     ×     2     ×     3     ×     2 = 24 
 HCF of 6, 12, 18 
 Firstly  ?nd  out  the  factors  of  6,  12,  18 
 and then multiply the common factors. 
 6 =  , 12 =  , 18 =  2     ×     3  2     ×     2     ×     3     2     ×     3     ×     3 
 HCF =  2     ×     3 = 6 
 Try  ?nding  HCF  and  LCM  of  3,  6,  9,  12 
 yourself.  HCF  of  3,  6,  9,  12  can  also  be 
 found  by  Division  method.  It  is  useful 
 when the numbers are bigger. 
 NOTE :- 
 (i).  HCF of A, B and C is the highest 
 divisor which can exactly divide 
 A, B, and C. 
 (ii).  LCM of A, B and C is the lowest 
 dividend which is exactly 
 divisible by A, B, and C. 
 There  is  one  very  important  relationship, 
 given  below,  between  two  numbers  and 
 their  HCF  and  LCM.  Many  problems  have 
 appeared  in  various  competitive  exams 
 based on this relationship. 
 Important Concepts:- 
 (1). 
 LCM × HCF = 1st number × 2nd number 
 Example:-  For numbers 8 and 12, 
 LCM = 24 and HCF = 4 
 Now, LCM  HCF = 24  4 = 96  ×    ×
 also, 8  12 = 96 ×
 (2).  HCF  of  some  numbers  is  always  a 
 factor of LCM of the numbers. 
 (3). 
 LCM of Fraction = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 (4). 
 HCF of Fraction = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 Example:  LCM and HCF of  ,  and 
 1 
 2 
 2 
 3 
 3 
 4 
 Solution:-  LCM = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 =  = 
 ??????     ????     1 , 2 ,       3 
 ??????     ????     2 , 3 , 4 
 6 
 1 
 HCF = 
 ??????     ????     ?????????????????? 
 ??????     ????     ?????????????????????? 
 =  = 
 ??????     ????     1 , 2 ,       3 
 ??????     ????     2 , 3 , 4 
 1 
 12 
 (5)  Co- Prime numbers : 
 If  the  HCF  of  two  numbers  is  1  then  they 
 are called co-prime numbers. 
 (6)  =  ; 
 ?????? 
 ?????? 
 ?????????????? 
 where LCM and HCF are of two numbers 
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 Pinnacle  Day:  6th - 7th  HCF and LCM 
 . If we ?nd two co-prime  ?? 
 1 
    ??????     ?? 
 2 
 factors,  , of the Product  ?? 
 1 
    ??????     ?? 
 2 
 as obtained above. 
 (7) 
 Example:- 
 (8). 
 If 1st number =  and 2nd  number =  ?? 
 1 
 ?? 
 2 
 HCF of  = Hx  ?? 
 1 
 HCF of  = Hy  ?? 
 2 
 And HCF of  and  = H  ?? 
 1 
 ?? 
 2 
 So , 
 Difference between  and  = Hx - Hy  ?? 
 1 
 ?? 
 2    
 = H(x - y) 
 Example :- 
 = 24 and  = 36  ?? 
 1 
 ?? 
 2 
 Note  :-  HCF  is  always  either  the 
 difference  of  two  numbers  or  factors  of 
 difference of two numbers. 
 (9).  When  the  second  divisor  is  a  factor 
 of  the  ?rst  divisor,  then  the  second 
 remainder  is  obtained  by  dividing  the  ?rst 
 remainder by the second divisor. 
 Example  :-  When  29  is  divided  by  8,  the 
 remainder  obtained  is  5,  then  what  will 
 be  the  remainder  when  the  same  number 
 is divided by 4 ? 
 Solution:-  Here,  the  second  divisor  that  is 
 4  is  a  factor  of  the  ?rst  divisor  that  is  8. 
 So,  on  dividing  the  ?rst  remainder  that  is 
 5  by  the  second  divisor  that  is  4,  we  get 
 our  second  remainder  which  is  1.  So,  the 
 required answer is 1. 
 Variety Questions 
 Q.1.  The LCM of x² - 8x + 15 and x² - 5x + 6 
 is: 
 SSC CPO 05/10/2023 (2nd Shift) 
 (a) (x + 5)(x + 2)(x + 3) 
 (b) (x - 5)(x - 2)(x - 3) 
 (c) (x + 5)(x - 2)(x - 3) 
 (d) (x - 2)(x - 3) 
 2 
 (x - 5) 
 Q.2.  The greatest possible length that 
 can  be  used  to  measure  exactly  the 
 lengths  of  3  m  15  cm,  5  m,  and  6  m  85 
 cm is: 
 SSC CPO 05/10/2023 (2nd Shift) 
 (a) 11 cm  (b) 7 cm  (c) 9 cm  (d) 5 cm 
 Q.3.  What is the HCF of (  + 1) and (  - 1)  ?? 
 6 
 ?? 
 4 
 SSC CPO 05/10/2023 (1st Shift) 
 (a) (1 +  )  (b) (1 + x)  (c) 1  (d) (1  )  ?? 
 2 
- ?? 
 2 
 Q.4.  The  LCM  of  two  prime  numbers  x 
 and y (x > y) is 533. The value of 4y - x is: 
 SSC CPO 03/10/2023 (3rd Shift) 
 (a) 11  (b) 21  (c) 18  (d) 23 
 Q.5.  What is the HCF of the polynomials 
 (  ³  -  8),  (  ³  -  6  ²  +  12  -  8)  and  (  ³  -  4  ²  +  4  ??  ??  ??  ??  ??  ?? 
 ) ?  ?? 
 SSC MTS 12/09/2023 (3rd Shift) 
 (a) (  - 1)  (b) (  - 2)  (c) (  - 8)  (d) (  - 4)  ??  ??  ??  ?? 
 Q.6.  Find  the  greatest  two  digit  number 
 which  on  dividing  219,  365,  511  leaves 
 the remainders 3, 5, 7, respectively. 
 SSC MTS 01/09/2023 (3rd Shift) 
 (a) 63  (b) 82  (c) 53  (d) 72 
 Q.7.  There  is  a  circular  path  around  a 
 sports  ?eld.  Rahul  takes  15  minutes  to 
 drive  one  round  of  the  ?eld,  while  Anil 
 takes  18  minutes  for  the  same.  Suppose 
 they  both  start  from  the  same  point  and 
 at  the  same  time,  and  go  in  the  same 
 direction.  After  how  many  minutes  will 
 they meet again at the starting point? 
 SSC MTS 11/05/2023 (Afternoon) 
 (a) 120  (b) 100  (c) 80  (d) 90 
 Q.8.  Let  x  =  224  and,  y  =  322.  If  the 
 highest  common  factor  of  23x  and  a  ×  y 
 is  divisible  by  x  and  y,  then  what  can  be 
 the possible value of a? 
 SSC CPO 11/11/2022 (Evening) 
 (a) 16  (b) 8  (c) 12  (d) 4 
 Q.9.  The  highest  common  factor  of  108, 
 72  and  5a  is  a.  What  can  be  the  least 
 common multiple of 108, 72 and a ? 
 SSC CPO 10/11/2022 (Afternoon) 
 (a) 432  (b) 324  (c) 108  (d) 216 
 Q.10.  What  is  the  greatest  positive 
 integer  that  divides  554,  714  and  213 
 leaving  the  remainder  43,  57  and  67, 
 respectively? 
 SSC CPO 10/11/2022 (Afternoon) 
 (a) 95  (b) 71  (c) 83  (d) 73 
 Q.11.  Find the HCF of (  – 1) and  4 
 315 
 (  – 1).  4 
 25 
 SSC MTS 26/07/2022 (Morning) 
 (a) 1    (b) (  – 1)    (c) 1024    (d) 1023  4 
 25 
 Q.12.  120  apples,  240  oranges  and  150 
 pears  are  packed  in  cartons  in  such  a 
 way  that  each  carton  has  the  same 
 number  of  fruits,  each  carton  contains 
 only  one  type  of  fruit  and  fruit  is  left 
 unpacked.  What  is  the  smallest  possible 
 number  of  cartons  needed  for  the 
 purpose ? 
 SSC MTS 08/07/2022 (Evening) 
 (a) 50  (b) 40  (c) 17  (d) 30 
 Q.13.  13,  a,  b,  c  are  four  distinct  numbers 
 and  the  HCF  of  each  pair  of  numbers  (13, 
 a)  :  (13,  b)  :  (13,  c)  is  13,  where  a,  b,  c  are 
 each  less  than  60  and  a  <  b  <  c.  What  is 
 the value of  ? 
 ??    +    ?? 
 ?? 
 SSC CGL 13/04/2021 (Morning) 
 (a) 3.5  (b) 2  (c) 5  (d) 4.5 
 Q.14.  The  sum  of  two  numbers  is  1215 
 and  their  HCF  is  81.  If  the  numbers  lie 
 between  500  and  700,  then  the  sum  of 
 reciprocals of the numbers is 
 SSC CPO 13/12/2019 (Evening) 
 (a)  (b)  (c)  (d) 
 5 
 1512 
 5 
 378 
 5 
 702 
 5 
 1188 
 Q.15.  If  r  is  the  remainder  when  each  of 
 6454,  7306  and  8797  is  divided  by  the 
 greatest number d (d > 1), then (d - r) is: 
 SSC CPO 13/12/2019 (Morning) 
 (a) 126    (b) 64    (c) 137    (d) 149 
 Q.16.  In  ?nding  the  HCF  of  two  numbers 
 by  division  method,  the  quotients  are  1,  8 
 and  2  respectively,  and  the  last  divisor  is 
 105, what is the sum of the numbers? 
 SSC CPO 11/12/2019 (Evening) 
 (a) 3570   (b) 3885   (c) 3780   (d) 3675 
 Q.17.  When  the  smallest  number  x  is 
 divided  by  5,  6,  8,  9  and  12,  it  gives 
 remainder  1  in  each  case.  But  x  is 
 divisible  by  13.  What  will  be  the 
 remainder when x will be divided by 31 
 SSC MTS 20/08/2019 (Afternoon) 
 (a) 1      (b) 5       (c) 3       (d) 0 
 Q.18.  The  Highest  Common  Factor  and 
 Lowest  Common  Multiple  of  two 
 numbers  p  and  q  are  A  and  B 
 respectively.  IF  A  +  B  =  p  +  q,  then  the 
 value of  is :  ?? 
 3 
+ ?? 
 3 
 SSC MTS 09/08/2019 (Evening) 
 (a)  p 
 3 
 (b)  q 
 3 
 (c)  p 
 3 
 +  q 
 3 
 (d)  p 
 3 
 -  q 
 3 
 Q.19.  What  is  the  largest  number  that 
 divides  460,  491  and  553  and  leaves  the 
 remainder 26 in each case ? 
 SSC MTS 06/08/2019 (Afternoon) 
 (a) 27      (b)35      (c) 33      (d) 31 
 Q.20.  A  is  the  smallest  three-digit 
 number  which  when  divided  by  3,  4  and  5 
 gives  remainder  1,  2  and  3  respectively. 
 What is the sum of the digits of A ? 
 SSC MTS 05/08/2019 (Afternoon) 
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 Pinnacle  Day:  6th - 7th  HCF and LCM 
 (a) 11  (b) 10  (c) 6       (d) 8 
 Q.21.  The  product  of  two  numbers  is 
 6760  and  their  HCF  is  13.  How  many 
 such pairs of numbers can be formed? 
 SSC CPO 16/03/2019 (Evening) 
 (a) 2         (b) 3          (c) 1         (d) 4 
 Q.22.  An  oil  merchant  has  3  varieties  of 
 oil  of  volumes  432,  594  and  702 
 respectively.  The  number  of  cans  of 
 equal  size  that  would  be  required  to  ?ll 
 the oil separately is: 
 SSC CPO 16/03/2019 (Afternoon) 
 (a) 13, 15, 17  (b) 8, 11, 13 
 (c) 8, 13, 15  (d) 6, 9, 11 
 Q.23.  Which  of  the  following  statements 
 is true ? 
 SSC CPO 14/03/2019 (Morning) 
 (a) LCM of two natural numbers is 
 divisible by their HCF. 
 (b) HCF + LCM of two numbers = 
 Product of the two numbers. 
 (c) Two prime numbers are co-prime 
 numbers if their LCM is 1. 
 (d) HCF of two numbers is the smallest 
 common divisor of both numbers. 
 Practice Questions 
 SSC CPO 2023 Tier - 1 
 Q.24.  The  largest  number  of  four  digits 
 that is exactly divisible by 17 and 36 is: 
 SSC CPO 03/10/2023 (1st Shift) 
 (a) 8568  (b) 9180  (c) 9792  (d) 7956 
 Q.25.  Two  numbers  are  in  the  ratio  3  :  4. 
 The  product  of  their  HCF  and  LCM  is 
 2700. The sum of the numbers is: 
 SSC CPO 03/10/2023 (1st Shift) 
 (a) 45  (b) 105  (c) 60  (d) 15 
 Q.26.  Find  the  greatest  number  which 
 when  divides  261,  853  and  1221,  leaves  a 
 remainder of 5 in each case. 
 SSC CPO 03/10/2023 (2nd  Shift) 
 (a) 18  (b) 17  (c) 16  (d) 19 
 Q.27.  Find the LCM of  ,  and  . 
 3 
 2 
 81 
 16 
 9 
 8 
 SSC CPO 03/10/2023 (2nd  Shift) 
 (a)  (b)  (c)  (d) 
 111 
 2 
 91 
 2 
 81 
 2 
 101 
 2 
 Q.28.  Find  the  greatest  possible  length 
 (in  metres)  that  can  be  used  to  exactly 
 measure  the  lengths  6  m,  5  m  25  cm  and 
 12 m 50 cm. 
 SSC CPO 03/10/2023 (2nd  Shift) 
 (a) 0.35 m (b) 0.90 m (c) 0.75 m (d) 0.25 m 
 Q.29.  The  least  number  which  should  be 
 added  to  1351  so  that  the  sum  is  exactly 
 divisible by 2, 4, 6 and 8 is: 
 SSC CPO 03/10/2023 (3rd Shift) 
 (a) 13  (b) 11  (c) 15  (d) 17 
 Q.30.  Two  numbers  are  in  the  ratio  of  4: 
 3.  The  product  of  their  HCF  and  LCM  is 
 2700.  The  difference  between  the 
 numbers is: 
 SSC CPO 03/10/2023 (3rd Shift) 
 (a) 25  (b) 30  (c) 15  (d) 105 
 Q.31.  Let  the  HCF  of  m  and  n  be  'a'  and 
 let n = ab, LCM of m and n is given by: 
 SSC CPO 04/10/2023 (1st Shift) 
 (a) ab  (b) am  (c) bm  (d) mn 
 Q.32.  The  LCM  and  HCF  of  two  numbers 
 are  1105  and  5.  If  the  LCM  is  17  times 
 the  ?rst  number,  then  ?nd  the  two 
 numbers. 
 SSC CPO 04/10/2023 (2nd Shift) 
 (a) 55 and 85  (b) 65 and 75 
 (c) 60 and 80  (d) 65 and 85 
 Q.33.  Which  is  the  smallest  natural 
 number  that  is  exactly  divisible  by  each 
 of 96, 108 and 144 ? 
 SSC CPO 04/10/2023 (2nd Shift) 
 (a) 1728   (b) 864   (c) 1296   (d) 2592 
 Q.34.  The HCF of 3888 and 3969 is: 
 SSC CPO 04/10/2023 (2nd Shift) 
 (a) 81  (b) 73  (c) 83  (d) 71 
 Q.35.  A  person  has  three  iron  bars  whose 
 lengths  are  20,  30  and  40  metres, 
 respectively.  He  wants  to  cut  pieces  of 
 the  same  length  from  each  of  the  three 
 bars.  What  is  the  least  number  of  total 
 pieces if he cuts without any wastage ? 
 SSC CPO 04/10/2023 (2nd Shift) 
 (a) 9  (b) 10  (c) 8  (d) 11 
 Q.36.  If  the  HCF  of  45  and  55  is 
 expressible  in  the  form  of  55  ×  5  +  45m, 
 then what is the value of m ? 
 SSC CPO 04/10/2023 (3rd Shift) 
 (a) 5   (b) –6   (c) –5   (d) 6 
 Q.37.  Find  the  least  number  which  when 
 divided  by  4,  9,  12  and  15,  leaves  the 
 remainder 3 in each case. 
 SSC CPO 04/10/2023 (3rd Shift) 
 (a) 193  (b) 183  (c) 360  (d) 180 
 Q.38.  Determine  the  LCM  of  two 
 numbers  if  their  HCF  is  12  and  their  ratio 
 is 13 : 15. 
 SSC CPO 04/10/2023 (3rd Shift) 
 (a) 2450   (b) 1780   (c) 1890   (d) 2340 
 Q.39.  What  is  the  smallest  perfect 
 square  number  which  is  completely 
 divisible by 4, 6, 9, 12 and 15? 
 SSC CPO 04/10/2023 (3rd Shift) 
 (a) 900  (b) 961  (c) 784  (d) 841 
 Q.40.  Which of the following numbers 
 leaves  the  remainder  equal  to  the  highest 
 common  factor  of  6,  8  and  9,  when 
 divided by 6, 8 and 9? 
 SSC CPO 04/10/2023 (3rd Shift) 
 (a) 506  (b) 575  (c) 291  (d) 433 
 Q.41.  Find  the  least  number  which  is 
 exactly divisible by 20, 28, 34, 60 and 75. 
 SSC CPO 05/10/2023 (1st Shift) 
 (a) 34500 (b) 35900 (c) 35700 (d) 36220 
 Q.42.  Three  numbers  are  in  the  ratio  of  5 
 :  7  :  9  and  their  LCM  is  34,650.  Their  HCF 
 is: 
 SSC CPO 05/10/2023 (1st Shift) 
 (a) 110  (b) 315  (c) 99  (d) 55 
 Q.43.  Which  is  the  largest  number  that 
 divides  each  of  1036,  1813  and  3885 
 without leaving any remainder ? 
 SSC CPO 05/10/2023 (1st Shift) 
 (a) 259  (b) 111  (c) 333  (d) 37 
 Q.44.  What  is  the  LCM  of  0.15,  0.18  and 
 0.45 ? 
 SSC CPO 05/10/2023 (2nd Shift) 
 (a) 0.6  (b) 0.9  (c) 0.81  (d) 0.09 
 Q.45.  What  will  be  the  least  number 
 which  when  doubled  will  be  exactly 
 divisible by 12, 14, 16 and 18 ? 
 SSC CPO 05/10/2023 (2nd Shift) 
 (a) 636  (b) 226  (c) 428  (d) 504 
 Q.46.  The  LCM  of  two  numbers  is  ?ve 
 times  their  HCF.  If  the  product  of  the  two 
 numbers  is  20480,  then  ?nd  their  HCF 
 and LCM, respectively. 
 SSC CPO 05/10/2023 (3rd Shift) 
 (a) 64 and 320  (b) 56 and 280 
 (c) 48 and 240  (d) 46 and 230 
 Q.47.  If  the  sum  of  two  numbers  is  60 
 and  their  HCF  and  LCM  are  5  and  60, 
 respectively,  then  the  sum  of  the 
 reciprocals of the numbers will be: 
 SSC CPO 05/10/2023 (3rd Shift) 
 (a)  (b)  (c)  (d) 
 1 
 4 
 1 
 5 
 1 
 11 
 1 
 6 
 Q.48.  Which  of  the  following  is  the 
 greatest  four-digit  number  that  is 
 divisible by 15, 25, 40, and 75? 
 SSC CPO 05/10/2023 (3rd Shift) 
 (a) 9000   (b) 9600   (c) 9500   (d) 9200 
 Q.49.  The  least  number  of  ?ve  digits 
 which  is  exactly  divisible  by  9,  12,  15,  25 
 and 27 is: 
 SSC CPO 05/10/2023 (3rd Shift) 
 (a) 10250 (b) 10800 (c) 10600 (d) 10700 
 SSC MTS 2023 Tier - 1 
 Q.50.  Three  measuring  tapes  are  64  cm 
 72 cm and 96 cm, respectively. What is 
 the least length that can be measured by 
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 Pinnacle  Day:  6th - 7th  HCF and LCM 
 any of the tapes exactly (in cm)? 
 SSC MTS 04/09/2023 (1st Shift) 
 (a) 575  (b) 570  (c) 576  (d) 525 
 Q.51.  What  is  the  largest  number  that 
 divides  627,  15630  and  3128  and  leaves 
 remainders of 2, 5 and 3, respectively? 
 SSC MTS 04/09/2023 (3rd Shift) 
 (a) 775  (b) 650  (c) 625  (d) 1225 
 Q.52.  The  HCF  of  three  numbers  is  57.  If 
 they  are  in  the  ratio  of  4  :  5  :  6,  then  ?nd 
 the numbers. 
 SSC MTS 05/09/2023 (2nd Shift) 
 (a) 228, 285, 342            (b) 236, 295, 354 
 (c) 240, 300, 360            (d) 232, 290, 348 
 Q.53.  Three  numbers  are  in  the  ratio  3  :  5 
 : 7 If their LCM is 2625, ?nd their HCF. 
 SSC MTS 05/09/2023 (3rd Shift) 
 (a) 100  (b) 125  (c) 50   (d) 25 
 Q.54.  Two  tankers  contain  850  litres  and 
 680  litres  of  oil.  Find  the  maximum 
 capacity  of  a  container  which  can 
 measure  the  oil  of  both  tankers  when 
 used, an exact number of times. 
 SSC MTS 06/09/2023 (2nd Shift) 
 (a) 425 litres  (b) 680 litres 
 (c) 340 litres  (d) 170 litres 
 Q.55.  The  largest  three-digit  number 
 which  gives  the  same  remainder  2  when 
 divided by 3, 5 and 9 is ________. 
 SSC MTS 08/09/2023 (1st Shift) 
 (a) 980  (b) 992  (c) 995  (d) 990 
 Q.56.  The LCM of  ,  ,  ,  is: 
 1    
 6    
 5    
 27    
 4    
 15       
 8    
 3       
 SSC MTS 08/09/2023 (3rd Shift) 
 (a)  (b)  (c)  (d) 
 40       
 3    
    3    
 28    
 5    
 28    
 40    
 5    
 Q.57.  Sanjay  wants  to  exactly  measure 
 the  lengths  7000  mm,  3850  mm  and 
 12950  mm  using  a  single  measuring 
 tape.  What  will  be  the  greatest  possible 
 length (in cm) of the measuring tape? 
 SSC MTS 11/09/2023 (2nd Shift) 
 (a) 40  (b) 45  (c) 35  (d) 30 
 Q.58.  Radha,  Pratima  and  Reena  begin  to 
 jog  around  a  circular  path  and  they 
 complete  their  revolutions  in  50  seconds, 
 75  seconds  and  100  seconds, 
 respectively.  After  how  much  time  (in 
 minutes)  will  they  meet  together  at  the 
 starting point for the ?rst time? 
 SSC MTS 11/09/2023 (3rd Shift) 
 (a) 6  (b) 5  (c) 4  (d) 3 
 Q.59.  The  HCF  of  two  numbers  is  12. 
 Which  of  the  following  can  never  be  their 
 LCM ? 
 SSC MTS 12/09/2023 (1st Shift) 
 (a) 24  (b) 74  (c) 48  (d) 60 
 Q.60.  The  product  of  two  numbers  is 
 4107.  If  the  HCF  of  these  numbers  is  37, 
 then the greater number is: 
 SSC MTS 12/09/2023 (2nd Shift) 
 (a) 111  (b) 74  (c) 185  (d) 37 
 Q.61.  Two numbers are in the ratio of 
 13  :  15.  If  their  HCF  is  3,  then  what  is  the 
 difference between these two numbers ? 
 SSC MTS 13/09/2023 (1st Shift) 
 (a) 4  (b) 2  (c) 8  (d) 6 
 Q.62.  The  LCM  of  the  two  numbers  is 
 1440  and  their  HCF  is  32.  If  the  ?rst 
 number  is  288,  then  ?nd  the  second 
 number. 
 SSC MTS 13/09/2023 (2nd Shift) 
 (a) 150  (b) 145  (c) 180  (d) 160 
 Q.63.  What  is  the  greatest  three-digit 
 number  which  when  divided  by  4,  8  and 
 9, leaves no remainder? 
 SSC MTS 13/09/2023 (3rd Shift) 
 (a) 924  (b) 963  (c) 932  (d) 936 
 Q.64.  Find  the  smallest  three  digit 
 number  which  when  added  to  5  is  exactly 
 divisible by 12, 14 and 18. 
 SSC MTS 14/09/2023 (2nd Shift) 
 (a) 240  (b) 225  (c) 245  (d) 247 
 Q.65.  The  ratio  of  two  numbers  is  3  :  4.  If 
 the  sum  of  these  two  numbers  is  70,  then 
 what is their LCM ? 
 SSC MTS 14/09/2023 (3rd Shift) 
 (a) 120  (b) 96  (c) 108  (d) 84 
 SSC CGL 2023 Tier - 1 
 Q.66.  Find  the  least  number  divisible  by 
 2,  3,  5,  6,  9  and  18,  which  is  a  perfect 
 square. 
 SSC CGL 24/07/2023 (2nd shift) 
 (a) 900  (b) 400  (c) 144  (d) 3600 
 SSC Selection Post (Phase - XI) 
 Q.67.  The  smallest  six-digit  number 
 which is divisible by 12, 16, 24, 28 is: 
 Matriculation Level 30/06/2023 (Shift - 3) 
 (a) 100128  (b) 100190 
 (c) 100180  (d) 100160 
 SSC CHSL 2022 Tier - 2 
 Q.68.  The  HCF  of  two  numbers  is 
 one-twentieth  of  their  LCM.  If  one  of  the 
 numbers  is  96  and  the  difference  of  the 
 LCM  and  the  HCF  is  456,  then  what  is  the 
 other number ? 
 SSC CHSL Tier II (26/06/2023) 
 (a) 48  (b) 120  (c) 144  (d) 72 
 SSC MTS 2022 Tier - 1 
 Q.69.  What is the HCF of two prime 
 numbers X and Y ? 
 SSC MTS 02/05/2023 (Morning) 
 (a) 1  (b) 2  (c) Y  (d) X 
 Q.70.  Two  numbers  are  in  the  ratio  11  :  6. 
 If  their  HCF  is  4,  ?nd  the  smallest 
 number. 
 SSC MTS 02/05/2023 (Afternoon) 
 (a) 30    (b) 18    (c) 24    (d) 12 
 Q.71.  Three  metal  rods  of  length  77  cm, 
 110  cm  and  121  cm  are  to  be  cut  into 
 parts  of  equal  length.  Each  part  must  be 
 as  long  as  possible.  What  is  the  maximum 
 number of pieces that can be cut? 
 SSC MTS 03/05/2023 (Morning) 
 (a) 18  (b) 28  (c) 11  (d) 21 
 Q.72.  What  is  that  least  number  that 
 should  be  added  to  478  so  that  the 
 number  obtained  becomes  exactly 
 divisible by 5, 6 and 12 ? 
 SSC MTS 04/05/2023 (Morning) 
 (a) 62  (b) 12  (c) 2  (d) 52 
 Q.73.  The  product  of  two  co-prime 
 numbers  is  483.  Find  the  Least  Common 
 Multiple of both numbers. 
 SSC MTS 08/05/2023 (Afternoon) 
 (a) 483  (b) 21  (c) 1  (d) 23 
 Q.74.  What  is  that  greatest  four-digit 
 number  which  when  divided  by  3  and  4 
 leaves remainder 2 in each case? 
 SSC MTS 09/05/2023 (Morning) 
 (a) 9994  (b) 9996  (c) 9998  (d) 9995 
 Q.75.  What  is  that  least  perfect  square 
 which  is  exactly  divisible  by  each  of  14, 
 84 and 28 ? 
 SSC MTS 10/05/2023 (Afternoon) 
 (a) 7056    (b) 3528     (c) 1764     (d) 441 
 Q.76.  Find  the  LCM  of  reciprocals  of  22 
 and 16. 
 SSC MTS 11/05/2023 (Evening) 
 (a)  (b)  (c)  (d) 
 1 
 2 
 1 
 3 
 1 
 6 
 1 
 4 
 Q.77.  The  greatest  number  which  when 
 divides  456  and  553  leaves  the 
 remainder as 6 and 3 respectively is: 
 SSC MTS 12/05/2023 (Evening) 
 (a) 5  (b) 50  (c) 10  (d) 30 
 Q.78.  The  least  number  which  when 
 divided  by  14,  18  and  36  and  leaves  1  as 
 remainder in each case is: 
 SSC MTS 16/05/2023 (Morning) 
 (a) 250  (b) 252  (c) 253  (d) 251 
 Q.79.  Three  numbers  are  in  the  ratio  2  :  3 
 :  5  and  their  LCM  is  60.  What  is  the  HCF 
 of the numbers? 
 SSC MTS 16/05/2023 (Evening) 
 (a) 2  (b) 4  (c) 10  (d) 6 
 Q.80.  Five bells commence tolling 
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 Pinnacle  Day:  6th - 7th  HCF and LCM 
 together  and  toll  at  intervals  of  5,  10,  15, 
 20  and  25  seconds  respectively.  In  1  hour 
 20  minutes,  how  many  times  do  they  toll 
 together? 
 SSC MTS 17/05/2023 (Afternoon) 
 (a) 20 times  (b) 15 times 
 (c) 14 times  (d) 17 times 
 Q.81.  What  will  be  the  ratio  of  the  Least 
 Common  Multiple  and  Highest  Common 
 Factor of 12, 24 and 36? 
 SSC MTS 13/06/2023 (Afternoon) 
 (a) 3 : 1   (b) 4 : 1   (c) 6 : 1   (d) 2 : 1 
 Q.82.  What  is  the  least  number  of 
 students  in  a  class  such  that  they  can 
 make  rows  of  10,  15  and  20  and  also  the 
 total  number  of  students  is  a  perfect 
 square? 
 SSC MTS 15/06/2023 (Morning) 
 (a) 6400   (b) 1600   (c) 900   (d) 1800 
 Q.83.  The  sum  of  the  two  numbers  is  45. 
 Their  HCF  and  LCM  are  5  and  70 
 respectively.  Find  the  sum  of  the 
 reciprocal of the two numbers. 
 SSC MTS 16/06/2023 (Afternoon) 
 (a)  (b)  (c)  (d) 
 9    
 70    
 3    
 140    
 4    
 35    
 3    
 16    
 Q.84.  What is the HCF of 513 and 1017 ? 
 SSC MTS 16/06/2023 (Evening) 
 (a) 15  (b) 8  (c) 9  (d) 13 
 Q.85.  The  Least  Common  Multiple  of 
 three  different  numbers  is  40.  Which  of 
 the  following  cannot  be  their  Highest 
 Common Factor ? 
 SSC MTS 19/06/2023 (Morning) 
 (a) 20  (b) 25  (c) 5  (d) 10 
 Q.86.  What  is  the  least  number  which 
 when  divided  by  8,  10,  12  and  18  leaves  a 
 remainder 5 in each case? 
 SSC MTS 20/06/2023 (Morning) 
 (a) 397  (b) 365  (c) 371  (d) 408 
 Q.87.  What  is  the  smallest  perfect  square 
 which is divisible by both 8 and 12 ? 
 SSC MTS 20/06/2023 (Afternoon) 
 (a) 100  (b) 144    (c) 121    (d) 196 
 Q.88.  The  length,  breadth,  height  of  a 
 room  is  6  m,  4  m  80  cm  and  3  m  60  cm 
 respectively.  Find  the  longest  tape  which 
 can  measure  the  dimensions  of  the  room 
 exactly. 
 SSC MTS 20/06/2023 (Evening) 
 (a) 1 m 40 cm  (b) 1m 20 cm 
 (c) 1 m 80 cm  (d) 1 m 50 cm 
 SSC CGL 2022 Tier - 2 
 Q.89.  The  product  of  the  two  numbers  is 
 1500  and  their  HCF  is  10.  The  number  of 
 such possible pairs is/are: 
 SSC CGL Tier II  (02/03/2023) 
 (a) 1  (b) 3  (c) 4  (d) 2 
 Q.90.  The  LCM  of  and  ??  ² - 8  ?? + 15    
 is:  ??  ² - 5  ?? + 6 
 SSC CGL Tier II  (03/03/2023) 
 (a) (  2)(  3)(  5)  ?? - ?? - ?? -
 (b) (  6)² (  + 1) (  - 3)  ?? - ??  ?? 
 (c) (  6) (  + 1)(  3)  ?? - ??  ?? -
 (d) (  + 6)(  + 1)(  3)  ??  ??  ?? -
 Q.91.  If  the  highest  common  factor 
 (HCF) of x and y is 15, then the HCF of 
 36  - 81  and  81  - 9  is  divisible by  ?? 
 2 
 ?? 
 2 
 ?? 
 2 
 ?? 
 2 
 SSC CGL Tier II  (06/03/2023) 
 (a) 135  (b) 120  (c) 180  (d) 90 
 SSC CGL 2022 Tier - 1 
 Q.92.  What  will  be  the  least  number 
 which  when  doubled  will  be  exactly 
 divisible by 15, 18, 25 and 32 ? 
 SSC CGL 02/12/2022 (2nd Shift) 
 (a) 3600  (b) 7200  (c) 6400  (d) 3200 
 Q.93.  Calculate the HCF of  ,  & 
 12 
 5 
 14 
 15 
 16 
 17 
 SSC CGL 03/12/2022 (1st Shift) 
 (a)  (b)  (c)  (d) 
 4 
 255 
 3 
 255 
 2 
 255 
 1 
 255 
 Q.94.  The  LCM  of  two  numbers  is  120 
 and  the  numbers  are  in  the  ratio  3  :  8. 
 The sum of the numbers will be: 
 SSC CGL 03/12/2022 (3rd Shift) 
 (a) 48  (b) 55  (c) 45  (d) 60 
 Q.95.  Choose  the  correct  statement  from 
 the following. 
 SSC CGL 06/12/2022 (2nd Shift) 
 (a) HCF is the least common multiple of 
 the given numbers. 
 (b) HCF of two or more numbers is the 
 highest number which perfectly 
 divides all the given numbers. 
 (c) HCF is also called the least common 
 divisor. 
 (d) In prime factorisation method of HCF, 
 the multiples of all the given numbers 
 are listed. 
 SSC CPO 2022 Tier - 1 
 Q.96.  The  least  common  multiple  of  a 
 and b is 42. The LCM of 5a and 11b is : 
 SSC CPO 09/11/2022 (Morning) 
 (a) 2310   (b) 4620   (c) 210   (d) 462 
 Q.97.  The  sum  of  two  numbers  is  1224 
 and their HCF is 68. The number of pairs 
 of  numbers  satisfying  the  above 
 condition is: 
 SSC CPO 09/11/2022 (Afternoon) 
 (a) 3  (b) 4  (c) 6  (d) 2 
 Q.98.  The sides of a triangular ?eld are 
 62  m,  186  m  and  279  m.  Find  the 
 greatest  length  of  tape  that  would  be 
 able  to  exactly  measure  each  of  them 
 without any fractions. 
 SSC CPO 10/11/2022 (Morning) 
 (a) 62 m  (b) 93 m   (c) 31 m  (d) 30 m 
 Q.99.  What is the LCM of 
 a 
 3 
 b - ab 
 3 
 , a 
 3 
 b 
 2 
 - a 
 2 
 b 
 3 
 , ab(a - b) ? 
 SSC CPO 11/11/2022 (Afternoon) 
 (a) a 
 2 
 b 
 2 
 (a 
 2 
 + b 
 2 
 )  (b) a 
 2 
 b 
 2 
 (a 
 2 
 - b 
 2 
 ) 
 (c) a 
 2 
 b 
 3 
 (a 
 2 
 + b 
 2 
 )  (d) a 
 3 
 b 
 2 
 (a 
 2 
 - b 
 2 
 ) 
 Q.100.  The  LCM  and  ratio  of  three 
 numbers  are  1386  and  3  :  7  :  11, 
 respectively. The sum of the greatest and 
 least numbers is: 
 SSC CPO 11/11/2022 (Evening) 
 (a) 60  (b) 64  (c) 84  (d) 108 
 SSC MTS 2021 Tier - 1 
 Q.101.  If  and  ?? = 2 
 8 
× 3 
 5 
,    ?? = 2 
 3 
× 3 
 4 
,
 ,  then  what  is  the  highest  ?? = 3 
 5 
× 2 
 7 
 common factor of P , Q and R? 
 SSC MTS 06/07/2022 (Afternoon) 
 (a)  (b)  2 
 3 
× 3 
 4 
 2 
 8 
× 3 
 5 
 (c)  (d)  2 
 2 
× 3 
 2 
 2 
 4 
× 3 
 5 
 Q.102.  The  tra?c  lights  at  3  different 
 road  crossings  change  after  every  48 
 sec,  72  sec  and  108  sec,  respectively.  If 
 they  all  change  simentionusly  at  8  :  20 
 a.m.,  then  at  what  will  they  next  change 
 again simultaneously? 
 SSC MTS 07/07/2022 (Morning) 
 (a) 8 : 27 : 12 a.m.   (b) 8 : 33 : 32 a.m. 
 (c) 8 : 12 : 18 a.m.   (d) 8 : 40 : 14 a.m. 
 Q.103.  The  ratio  of  the  LCM  of  two 
 numbers  to  the  sum  of  the  same  two 
 numbers  is  12  :  7.  If  their  HCF  is  4,  what 
 is the product of these two numbers? 
 SSC MTS 14/07/2022 (Morning) 
 (a) 192  (b) 172  (c) 196  (d) 169 
 Q.104.  P  =  2 
 5 
 3 
 8 
 and  Q  =  2 
 3 
 3 
 K 
 .  If  the × ×
 highest  common  factor  of  P  and  Q  is  2 
 3 
 3 
 3 
 , then what is the value of K ? ×
 SSC MTS 15/07/2022 (Morning) 
 (a) 1  (b) 2  (c) 3  (d) 5 
 Q.105.  If  and  are  two  distinct  prime  ?? 
 1 
 ?? 
 2 
 numbers,  then  what  is  the  product  of  the 
 highest  common  factor  and  the  least 
 common multiple of  and  ?  ?? 
 1 
 ?? 
 2 
 SSC MTS 20/07/2022 (Afternoon) 
 (a) 1   (b)  (c)  +  (d) 
 ?? 
 1 
   
 ?? 
 2 
   
 ?? 
 1 
 ?? 
 2 
 ?? 
 1 
× ?? 
 2 
 Q.106.  Two  wires  of  lengths  10  m  54  cm 
 and  11  m  56  cm  are  both  cut  into  pieces 
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FAQs on SSC CGL Previous Year Questions (2023 - 18): HCF & LCM - SSC CGL Mathematics Previous Year Paper (Topic-wise)

1. What is the difference between HCF and LCM?
Ans.HCF (Highest Common Factor) is the largest number that divides two or more numbers without leaving a remainder, while LCM (Lowest Common Multiple) is the smallest number that is a multiple of two or more numbers.
2. How can I calculate the HCF of two numbers using prime factorization?
Ans.To calculate the HCF using prime factorization, first, express both numbers as products of prime factors. Then, identify the common prime factors and multiply them together to get the HCF.
3. What is the relationship between HCF and LCM of two numbers?
Ans.The relationship between HCF and LCM of two numbers can be expressed as: HCF × LCM = Product of the two numbers. This means that if you know the HCF and one of the numbers, you can find the LCM easily.
4. How can I find the LCM of three or more numbers?
Ans.To find the LCM of three or more numbers, you can use the prime factorization method for each number and then take the highest power of each prime factor that appears in the factorizations. Multiply these together to get the LCM.
5. Are there any shortcuts to calculate HCF and LCM for large numbers?
Ans.Yes, for large numbers, you can use the Euclidean algorithm to find the HCF quickly. For LCM, you can use the formula LCM(a, b) = (a × b) / HCF(a, b) to simplify the calculation.
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