All Exams  >   Class 6  >   Maths Olympiad Class 6  >   All Questions

All questions of Playing with Numbers for Class 6 Exam

Which greatest number of 4 digits is exactly divisible by 12, 16, 28 & 36?
  • a)
    6072
  • b)
    8072
  • c)
    8972
  • d)
    9072
Correct answer is option 'D'. Can you explain this answer?

Shreya Sarkar answered
Here is the answer.

LCM of 12, 16, 24, 28 and 36

12= 3x2x2
16=2x2x2x2
24=2x2x2x3
28=2x2x7
36=2x2x3x3

so, LCM is 2x2x2x2x3x3x7= 1008

And the greatest 4-digit no. is 9999

so, dividing 9999 by 1008 we get, 9 as quotient and 927 as reminder .

So, the largest 4-digit no. divisible by all these nos. is 9999-927= 9072.

Which of the following is not a twin prime?
  • a)
    (11, 13)
  • b)
    (17, 19)
  • c)
    (23, 31)
  • d)
    (41, 43) 
Correct answer is option 'C'. Can you explain this answer?

Anita Menon answered
(23, 31) is not a twin prime. 
twin prime is a prime number that is either 2 less or 2 more than another prime number—for example, either member of the twin prime pair (17, 19) or (41, 43).

The smallest number which when diminished by 3 is divisible by 21, 28, 36 and 45 is
  • a)
    1163
  • b)
    1263
  • c)
    1283
  • d)
    1293
Correct answer is option 'B'. Can you explain this answer?

Rohini khanna answered
LCM of 21, 28, 36 and 45 is

∴ LCM of 21, 28, 36 and 45
= 3 × 2 × 3 × 2 × 7 × 5
= 36 × 35 
= 1260
∴ Required number = 1260 + 3 = 1263

What is sum of first five multiples of 23?
  • a)
    341
  • b)
    342
  • c)
    343
  • d)
    345
Correct answer is option 'D'. Can you explain this answer?

Sum of first five multiples of 23 = 23 + 23 × 2 + 23 × 3 + 23 × 4 + 23 × 5 
= 23 (1 + 2 + 3 + 4 + 5)
= 23 × 15 
= 345 

Which of the following number is not divisible by 9?
  • a)
    387459
  • b)
    904806
  • c)
    758934
  • d)
    879134
Correct answer is option 'D'. Can you explain this answer?

3 + 8 + 7 + 4 + 5 + 9 = 36
9 + 0 + 4 + 8 + 0 + 6 = 27
7 + 5 + 8 + 9 +3 + 4 = 36
8 + 7 + 9 + 1 + 3 + 4 = 32
∴ 32 is not divisible by 9.
∴ 879134 is not divisible 9.

Four bells ring at intervals of 6, 8, 12 & 20 minutes. They ring simultaneously at 7 a.m. At what time will they ring together?
  • a)
    8 a.m.
  • b)
    9 a.m.
  • c)
    10 a.m.
  • d)
    9:30 a.m. 
Correct answer is option 'B'. Can you explain this answer?

Varun Kapoor answered
Required time = LCM of 6, 8, 12 and 20

∴ Required time = 2 × 2 × 3 × 2 × 5
= 120 minutes = 2 hr.
∴ bell will again ring together at (7 + 2)
= 9 a.m.

What is the maximum even multiple of 25 between 500 & 700?
  • a)
    660
  • b)
    600
  • c)
    675
  • d)
    650
Correct answer is option 'D'. Can you explain this answer?

Sushil Kumar answered
When we divide 650 by 2 and 25 we get whole number, it is not possible with other options. so option d is correct.

The HCF of two numbers is 145 and their LCM is 2175. If one of the numbers is 725. What is the other number?
  • a)
    5
  • b)
    290
  • c)
    115
  • d)
    435
Correct answer is option 'D'. Can you explain this answer?

Subham Nair answered
HCF of two numbers = 145 

LCM of two numbers = 2175 

Let one of the two numbers be 725 and other be x. 

Using the formula, product of two numbers = HCF x LCM 

we conclude that 

725 x x= 145 x 2175 

x = 145 x2175/ 725 

= 435 

Hence, the other number is 435.

Four bells toll at intervals 4, 7, 12 & 84 seconds. The bells toll together at 7 o’clock. How many times will they again toll together in 28 minutes?
  • a)
    15
  • b)
    20
  • c)
    25
  • d)
    30
Correct answer is option 'B'. Can you explain this answer?

They will toll together for a 'common multiple' of (4,7,12,84), which is the l.c.m of these numbers.
4= 2^2
7 = 7
12 = 2^2 * 3
84 = 12 * 7 = 2^2 * 3 * 7
l.c.m(4,7,12,84) = 2^2 * 3 * 7 = 84 s
84 s = 1 min 24 sec
Hence they will toll together 84 seconds after 5 o'clock or 5:01:24 hrs ( 1 min 24 sec past 5 o'clock)
28 mins = 28*60 = 1680 sec
84 sec== toll 1 time
1680 sec== X times
X = 20 times
Hence,
They toll together at 5:01:24 hrs
In 28 mins they toll (together) 20 times.

Which of the following numbers is divisible by 3?
  • a)
    24357806
  • b)
    33336433
  • c)
    35769812
  • d)
    83479560 
Correct answer is option 'D'. Can you explain this answer?

Dhruv Malik answered
2 + 4 + 3 + 5 + 7 + 8 + 0 + 6 = 35
3 + 3 + 3 + 3 + 6  + 4 + 3 + 3 = 28
3 + 5 + 7 + 6 + 9 + 8 + 1 + 2 = 41 
8 + 3 + 4 + 7 + 9 + 5 + 6 + 0 = 42
Since 42 is divisible by 3 then (d) is divisible by 3. 

Find the largest number that will divide 76, 113 and 186 leaving remainder 4, 5, 6 respectively.
  • a)
    24
  • b)
    12
  • c)
    36
  • d)
    54
Correct answer is option 'C'. Can you explain this answer?

Debanshi Roy answered
Solution:
The largest number that will divide 76, 113 and 186 leaving remainder 4, 5, 6 respectively is also known as the highest common factor (HCF) of (76-4), (113-5) and (186-6).

Step-by-step solution:
• Subtract the remainder from each number to get the actual number.
• So, the actual numbers are 72, 108, and 180.
• Now, find the common factors of these numbers.
• The common factors of 72, 108, and 180 are 1, 2, 3, 4, 6, 9, 12, 18, 36.
• Out of these common factors, select the highest one which leaves the same remainder when divided by 4, 5, and 6 respectively.
• The highest common factor (HCF) of (76-4), (113-5) and (186-6) is 36.
• Hence, the correct option is (c) 36.

Therefore, the largest number that will divide 76, 113 and 186 leaving remainder 4, 5, 6 respectively is 36.

Find the smallest possible number which on adding 19 becomes exactly divisible by 28, 36 and 45.
  • a)
    1239
  • b)
    1241
  • c)
    1243
  • d)
    1245
Correct answer is option 'B'. Can you explain this answer?

Solution:
45 x 28 = 1, 260
36 x 35 = 1, 260
28 x 45 = 1, 260

Least Common Multiple (LCM) of 28, 36, and 45 is 1, 260
So, 1, 260 subtracted by 19 (smallest number which on adding 19)
will be 1, 241

Answer: 1, 241

LCM or the Least Common Multiple is the terminology for the common or similar multiple/s of more than one numbers.

1870 is divisible by 22. Which two numbers nearest to 1870 are each divisible by 22?
  • a)
    1848, 1892
  • b)
    1893, 1914
  • c)
    1826, 1914
  • d)
    None of these 
Correct answer is option 'A'. Can you explain this answer?

To determine the two numbers nearest to 1870 that are each divisible by 22, we can use the concept of divisibility and apply it to the given options.

Divisibility Rule of 22: A number is divisible by 22 if it is divisible by both 2 and 11.

Let's analyze the given options one by one to see if they satisfy the divisibility rule of 22.

a) 1848, 1892:
- 1848: This number is divisible by 2 because the last digit is even (8). However, to determine if it is divisible by 11, we can use the divisibility rule of 11, which states that the difference between the sum of the digits in the odd place and the sum of the digits in the even place should be either 0 or a multiple of 11.
- In this case, 1 - 8 + 4 - 8 = -11, which is a multiple of 11. Therefore, 1848 is divisible by 11 and consequently divisible by 22.
- 1892: This number is divisible by 2 because the last digit is even (2). However, to determine if it is divisible by 11, we can use the divisibility rule of 11.
- In this case, 1 - 8 + 9 - 2 = 0, which is a multiple of 11. Therefore, 1892 is divisible by 11 and consequently divisible by 22.

Since both 1848 and 1892 satisfy the divisibility rule of 22, option A is correct.

b) 1893, 1914:
- 1893: This number is not divisible by 2 because the last digit is odd (3). Therefore, it is not divisible by 22.
- 1914: This number is divisible by 2 because the last digit is even (4). However, it is not divisible by 11 since 1 - 9 + 1 - 4 = -11, which is not a multiple of 11. Therefore, it is not divisible by 22.

Option B is incorrect.

c) 1826, 1914:
- 1826: This number is divisible by 2 because the last digit is even (6). However, it is not divisible by 11 since 1 - 8 + 2 - 6 = -11, which is not a multiple of 11. Therefore, it is not divisible by 22.
- 1914: This number is divisible by 2 because the last digit is even (4). However, it is not divisible by 11 since 1 - 9 + 1 - 4 = -11, which is not a multiple of 11. Therefore, it is not divisible by 22.

Option C is incorrect.

d) None of these:
Since we have found that option A is correct, option D is incorrect.

Therefore, the two numbers nearest to 1870 that are each divisible by 22 are 1848 and 1892, as stated in option A.

Find the greatest 3-digit number which is divisible by 8, 10 and 12.
  • a)
    840
  • b)
    480
  • c)
    960
  • d)
    980
Correct answer is option 'C'. Can you explain this answer?

Gayatri Roy answered
L.C.M of 8, 10, 12 = 2 x 2 x 2 x 3 x 5 = 120


We have to find the greatest 3 digit multiple of 120


It can be seen that 120 x 8 =960 and 120 x 9 =1080.


Hence, the greatest 3- digit number exactly divisible by 8 , 10 and 12 is 960

What is the least 5-digit number which is exactly divisible by 20, 25, 30?
  • a)
    10200
  • b)
    10300
  • c)
    10400
  • d)
    10100
Correct answer is option 'A'. Can you explain this answer?

LCM of 20, 25, 30 is

∴ LCM of 20, 25, 30 = 2 × 5 × 2 × 5 × 3
= 300
∴ Ieast 5-digit number which is exactly divisible by 20, 25, 30 = 10200.

In 467 * 381 replace * by which smallest digit to make it divisible by 3?
  • a)
    1
  • b)
    2
  • c)
    3
  • d)
    4
Correct answer is option 'A'. Can you explain this answer?

Veena Menon answered
467 * 381 
The sum of digits of the above number
= 4 + 6 + 7 + * + 3 + 8 + 1
= 10 + 7 + * + 3 + 8 + 1
= 29 + *
If, ∗  = 1, then, the sum of digits will become 30.
∴ required number = 1

The HCF of two numbers is 23 and their LCM is 1449. If one of the numbers is 161 what is the other?
  • a)
    107
  • b)
    117
  • c)
    167
  • d)
    207
Correct answer is option 'D'. Can you explain this answer?

Harshad Goyal answered
To find the other number, we can use the formula:

LCM × HCF = Product of the two numbers

Given that the HCF is 23 and the LCM is 1449, we can substitute these values into the formula:

1449 × 23 = Product of the two numbers

Therefore, the product of the two numbers is 33327.

We are also given that one of the numbers is 161. Let's call the other number x.

So, the equation becomes:

161 × x = 33327

To find the value of x, we can divide both sides of the equation by 161:

x = 33327 ÷ 161

Performing the division, we get:

x ≈ 207

Therefore, the other number is approximately 207.

Hence, the correct answer is option D) 207.

The greatest number that will divide 445, 572 & 699 leaving remainder 4, 5, 6 respectively.
  • a)
    84
  • b)
    42
  • c)
    49
  • d)
    63
Correct answer is option 'D'. Can you explain this answer?

Shruti Mishra answered
Solution-> 445 - 4 = 441 
                 572 - 5 = 567 
                 699 - 6 = 693 

Now find the greatest common factor of those 3 numbers: 
441 = 3 x 3 x 7 x 7 
572 = 3 x 3 x 3 x 3 x 7 
693 = 3 x 3 x 7 x 11 

The common factors are 3 x 3 x 7 = 63 
HCF Of (441,567,693) = 63 

445 / 63 = 7 remainder 4 
572 / 63 = 9 remainder 5 
699 / 63 = 11 remainder 6 

63 is the largest divisor that will give the desired remainders.

Chapter doubts & questions for Playing with Numbers - Maths Olympiad Class 6 2025 is part of Class 6 exam preparation. The chapters have been prepared according to the Class 6 exam syllabus. The Chapter doubts & questions, notes, tests & MCQs are made for Class 6 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests here.

Chapter doubts & questions of Playing with Numbers - Maths Olympiad Class 6 in English & Hindi are available as part of Class 6 exam. Download more important topics, notes, lectures and mock test series for Class 6 Exam by signing up for free.

Maths Olympiad Class 6

8 videos|113 docs|60 tests

Signup to see your scores go up within 7 days!

Study with 1000+ FREE Docs, Videos & Tests
10M+ students study on EduRev