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Class 10 Mathematics: CBSE (Official) Marking Scheme with Solutions (2017-18) | Mathematics (Maths) Class 10 PDF Download

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 Page 1


 
 
Marking Scheme  
Mathematics Class X (2017-18) 
Section A 
S.No. Answer Marks 
1. Non terminating repeating decimal expansion.  [1] 
2. k = ±4 [1] 
3. a
11
 = –25 [1] 
4. (0, 5) [1] 
5. 9 : 49 [1] 
6. 25 [1] 
 
Section B 
7. LCM (p, q) = a
3
b
3
  
HCF (p, q) = a
2
b 
LCM (p, q) × HCF (p, q) = a
5
b
4
 = (a
2
b
3
) (a
3
 b) = pq 
[1/2] 
[1/2] 
[1] 
8. S
n
 = 2n
2
 + 3n 
S
1
 = 5 = a
1 
S
2
 = a
1
 + a
2
 = 14 ? a
2
 = 9 
d = a
2
 – a
1
= 4 
a
16
 = a
1
 + 15d = 5 + 15(4) = 65 
[1/2] 
[1/2] 
[1/2] 
 
[1/2] 
9. For pair of equations kx + 1y = k
2
 and 1x + ky = 1 
We have:  
2
1 1 1
2 2 2
a k b 1 c k
,,
a 1 b k c 1
? ? ?
 
For infinitely many solutions, 
1 1 1
2 2 2
a b c
a b c
??
 
? 
2
k1
k 1 k 1, –1
1k
? ? ? ? ?
              
...(i) 
 and 
2
3
1k
k 1 k 1
k1
? ? ? ? ?              ...(ii)                  …(ii) 
From (i) and (ii), k = 1 
 
 
 
 
 
[1/2] 
 
[1/2] 
 
[1/2] 
 
[1/2] 
10. 
Since 
p
1,
3
??
??
??
 is the mid-point of the line segment joining the points (2, 0) and 
2
0,
9
??
??
??
 therefore, 
2
0
p1
9
p
3 2 3
?
? ? ?
 
The line 5x + 3y + 2 = 0 passes through the point (–1, 1) as 5(–1) + 3(1) + 2 = 0 
 
 
 
 
[1] 
 
[1] 
11. 
(i) P(square number) = 
8
113
 
(ii) P(multiple of 7) = 
16
113
 
 
[1] 
 
[1] 
Page 2


 
 
Marking Scheme  
Mathematics Class X (2017-18) 
Section A 
S.No. Answer Marks 
1. Non terminating repeating decimal expansion.  [1] 
2. k = ±4 [1] 
3. a
11
 = –25 [1] 
4. (0, 5) [1] 
5. 9 : 49 [1] 
6. 25 [1] 
 
Section B 
7. LCM (p, q) = a
3
b
3
  
HCF (p, q) = a
2
b 
LCM (p, q) × HCF (p, q) = a
5
b
4
 = (a
2
b
3
) (a
3
 b) = pq 
[1/2] 
[1/2] 
[1] 
8. S
n
 = 2n
2
 + 3n 
S
1
 = 5 = a
1 
S
2
 = a
1
 + a
2
 = 14 ? a
2
 = 9 
d = a
2
 – a
1
= 4 
a
16
 = a
1
 + 15d = 5 + 15(4) = 65 
[1/2] 
[1/2] 
[1/2] 
 
[1/2] 
9. For pair of equations kx + 1y = k
2
 and 1x + ky = 1 
We have:  
2
1 1 1
2 2 2
a k b 1 c k
,,
a 1 b k c 1
? ? ?
 
For infinitely many solutions, 
1 1 1
2 2 2
a b c
a b c
??
 
? 
2
k1
k 1 k 1, –1
1k
? ? ? ? ?
              
...(i) 
 and 
2
3
1k
k 1 k 1
k1
? ? ? ? ?              ...(ii)                  …(ii) 
From (i) and (ii), k = 1 
 
 
 
 
 
[1/2] 
 
[1/2] 
 
[1/2] 
 
[1/2] 
10. 
Since 
p
1,
3
??
??
??
 is the mid-point of the line segment joining the points (2, 0) and 
2
0,
9
??
??
??
 therefore, 
2
0
p1
9
p
3 2 3
?
? ? ?
 
The line 5x + 3y + 2 = 0 passes through the point (–1, 1) as 5(–1) + 3(1) + 2 = 0 
 
 
 
 
[1] 
 
[1] 
11. 
(i) P(square number) = 
8
113
 
(ii) P(multiple of 7) = 
16
113
 
 
[1] 
 
[1] 
 
 
12. Let number of red balls be = x 
? P(red ball) = 
x
12
 
If 6 more red balls are added: 
The number of red balls = x + 6 
P(red ball) = 
x6
18
?
 
Since,  
x 6 x
2 x 3
18 12
? ??
? ? ?
??
??
 
? There are 3 red balls in the bag. 
 
 
 
[1/2] 
 
 
 
[1] 
 
 
[1/2] 
 
Section C 
13. Let n = 3k, 3k + 1 or 3k + 2. 
(i) When n = 3k: 
 n is divisible by 3. 
 n + 2 = 3k + 2 ? n + 2 is not divisible by 3. 
 n + 4 = 3k + 4 = 3(k + 1) + 1 ? n + 4 is not divisible by 3. 
(ii) When n = 3k + 1: 
 n is not divisible by 3. 
 n + 2 = (3k + 1) + 2 = 3k + 3 = 3(k + 1) ?  n + 2 is divisible by 3. 
 n + 4 = (3k + 1) + 4 = 3k + 5 = 3(k + 1) + 2 ? n + 4 is not divisible by 3. 
(iii) When n = 3k + 2: 
 n is not divisible by 3. 
 n + 2 = (3k + 2) + 2 = 3k + 4 = 3(k + 1) + 1 ? n + 2 is not divisible by 3. 
 n + 4 = (3k + 2) + 4 = 3k + 6 = 3(k + 2) ? n + 4 is divisible by 3. 
 Hence exactly one of the numbers n, n + 2 or n + 4 is divisible by 3. 
 
 
 
 
[1] 
 
 
 
[1] 
 
 
 
 
[1] 
14. 
Since 
55
and
33
? are the two zeroes therefore, 
2
5 5 1
x x (3x 5)
3 3 3
? ? ? ?
? ? ? ?
? ? ? ?
? ? ? ?
? ? ? ?
 
is a factor of given polynomial. 
We divide the given polynomial by 3x
2
 – 5. 
                                                     x
2
 + 2x + 1 
               
For other zeroes, x
2
 + 2x + 1 = 0 ? (x + 1)
2
 = 0, x = –1, –1  
? Zeroes of the given polynomial are 
55
, , –1and –1
33
? . 
 
[1] 
 
 
 
 
 
 
 
 
 [1] 
 
 
 
 
 
 
 
 [1] 
Page 3


 
 
Marking Scheme  
Mathematics Class X (2017-18) 
Section A 
S.No. Answer Marks 
1. Non terminating repeating decimal expansion.  [1] 
2. k = ±4 [1] 
3. a
11
 = –25 [1] 
4. (0, 5) [1] 
5. 9 : 49 [1] 
6. 25 [1] 
 
Section B 
7. LCM (p, q) = a
3
b
3
  
HCF (p, q) = a
2
b 
LCM (p, q) × HCF (p, q) = a
5
b
4
 = (a
2
b
3
) (a
3
 b) = pq 
[1/2] 
[1/2] 
[1] 
8. S
n
 = 2n
2
 + 3n 
S
1
 = 5 = a
1 
S
2
 = a
1
 + a
2
 = 14 ? a
2
 = 9 
d = a
2
 – a
1
= 4 
a
16
 = a
1
 + 15d = 5 + 15(4) = 65 
[1/2] 
[1/2] 
[1/2] 
 
[1/2] 
9. For pair of equations kx + 1y = k
2
 and 1x + ky = 1 
We have:  
2
1 1 1
2 2 2
a k b 1 c k
,,
a 1 b k c 1
? ? ?
 
For infinitely many solutions, 
1 1 1
2 2 2
a b c
a b c
??
 
? 
2
k1
k 1 k 1, –1
1k
? ? ? ? ?
              
...(i) 
 and 
2
3
1k
k 1 k 1
k1
? ? ? ? ?              ...(ii)                  …(ii) 
From (i) and (ii), k = 1 
 
 
 
 
 
[1/2] 
 
[1/2] 
 
[1/2] 
 
[1/2] 
10. 
Since 
p
1,
3
??
??
??
 is the mid-point of the line segment joining the points (2, 0) and 
2
0,
9
??
??
??
 therefore, 
2
0
p1
9
p
3 2 3
?
? ? ?
 
The line 5x + 3y + 2 = 0 passes through the point (–1, 1) as 5(–1) + 3(1) + 2 = 0 
 
 
 
 
[1] 
 
[1] 
11. 
(i) P(square number) = 
8
113
 
(ii) P(multiple of 7) = 
16
113
 
 
[1] 
 
[1] 
 
 
12. Let number of red balls be = x 
? P(red ball) = 
x
12
 
If 6 more red balls are added: 
The number of red balls = x + 6 
P(red ball) = 
x6
18
?
 
Since,  
x 6 x
2 x 3
18 12
? ??
? ? ?
??
??
 
? There are 3 red balls in the bag. 
 
 
 
[1/2] 
 
 
 
[1] 
 
 
[1/2] 
 
Section C 
13. Let n = 3k, 3k + 1 or 3k + 2. 
(i) When n = 3k: 
 n is divisible by 3. 
 n + 2 = 3k + 2 ? n + 2 is not divisible by 3. 
 n + 4 = 3k + 4 = 3(k + 1) + 1 ? n + 4 is not divisible by 3. 
(ii) When n = 3k + 1: 
 n is not divisible by 3. 
 n + 2 = (3k + 1) + 2 = 3k + 3 = 3(k + 1) ?  n + 2 is divisible by 3. 
 n + 4 = (3k + 1) + 4 = 3k + 5 = 3(k + 1) + 2 ? n + 4 is not divisible by 3. 
(iii) When n = 3k + 2: 
 n is not divisible by 3. 
 n + 2 = (3k + 2) + 2 = 3k + 4 = 3(k + 1) + 1 ? n + 2 is not divisible by 3. 
 n + 4 = (3k + 2) + 4 = 3k + 6 = 3(k + 2) ? n + 4 is divisible by 3. 
 Hence exactly one of the numbers n, n + 2 or n + 4 is divisible by 3. 
 
 
 
 
[1] 
 
 
 
[1] 
 
 
 
 
[1] 
14. 
Since 
55
and
33
? are the two zeroes therefore, 
2
5 5 1
x x (3x 5)
3 3 3
? ? ? ?
? ? ? ?
? ? ? ?
? ? ? ?
? ? ? ?
 
is a factor of given polynomial. 
We divide the given polynomial by 3x
2
 – 5. 
                                                     x
2
 + 2x + 1 
               
For other zeroes, x
2
 + 2x + 1 = 0 ? (x + 1)
2
 = 0, x = –1, –1  
? Zeroes of the given polynomial are 
55
, , –1and –1
33
? . 
 
[1] 
 
 
 
 
 
 
 
 
 [1] 
 
 
 
 
 
 
 
 [1] 
 
 
15. Let the ten’s and the units digit be y and x respectively. 
So, the number is 10y + x. 
The number when digits are reversed is 10x + y. 
Now, 7(10y + x) = 4(10x + y) ? 2y = x             …(i)  
Also x – y = 3                                                      …(ii) 
Solving (1) and (2), we get y = 3 and x = 6. 
Hence the number is 36. 
 
[1/2] 
[1/2] 
[1] 
[1/2] 
 
[1/2] 
16. Let x-axis divides the line segment joining (–4, –6) and (–1, 7) at the point P in the 
ratio 1 : k. 
Now, coordinates of point of division 
–1– 4k 7 – 6k
P,
k 1 k 1
??
??
??
??
 
Since P lies on x-axis, therefore 
7 6k
0
k1
?
?
?
 
                                                        
? 7 – 6k = 0 
                                                        
?  k = 
7
6
 
Hence the ratio is 
7
1: 6 : 7
6
?  
Now, the coordinates of  P are 
34
,0
13
???
??
??
. 
OR 
Let the height of parallelogram taking AB as base be h. 
Now AB = 
2 2 2 2
(7 4) (2 2) 3 4 5 units ? ? ? ? ? ? . 
Area ( ? ABC) = ? ?
1 49
4(2 – 9) 7(9 2) 0(–2 – 2) sq units
22
? ? ? ? . 
Now,  
1 49
AB h
22
? ? ? ? 
 
? 
1 49
5h
22
? ? ? ? 
? ?h = 
49
9.8 units
5
? . 
 
[1/2] 
 
 
 
[1] 
 
 
 
 
[1/2] 
 
[1] 
 
 
 
 
[1] 
 
[1] 
 
 
 
 
 
 
[1] 
17. ? SQN = ? TRM    (CPCT as NSQ MTR) ? ? ? 
 
Since, P 1 2 ? ? ? ? ? = P PQR PRQ ? ? ? ? ?    (Angle sum property) 
? 12 ? ? ? = PQR PRQ ? ? ? 
? 2 1 2 PQR ? ? ?  (as 1 2 and PQR PRQ) ? ? ? ? ? ? ? ?  
1 ? = PQR ? 
[1] 
 
 
 
 
 
 
 
 
 
 
 [1] 
 
Page 4


 
 
Marking Scheme  
Mathematics Class X (2017-18) 
Section A 
S.No. Answer Marks 
1. Non terminating repeating decimal expansion.  [1] 
2. k = ±4 [1] 
3. a
11
 = –25 [1] 
4. (0, 5) [1] 
5. 9 : 49 [1] 
6. 25 [1] 
 
Section B 
7. LCM (p, q) = a
3
b
3
  
HCF (p, q) = a
2
b 
LCM (p, q) × HCF (p, q) = a
5
b
4
 = (a
2
b
3
) (a
3
 b) = pq 
[1/2] 
[1/2] 
[1] 
8. S
n
 = 2n
2
 + 3n 
S
1
 = 5 = a
1 
S
2
 = a
1
 + a
2
 = 14 ? a
2
 = 9 
d = a
2
 – a
1
= 4 
a
16
 = a
1
 + 15d = 5 + 15(4) = 65 
[1/2] 
[1/2] 
[1/2] 
 
[1/2] 
9. For pair of equations kx + 1y = k
2
 and 1x + ky = 1 
We have:  
2
1 1 1
2 2 2
a k b 1 c k
,,
a 1 b k c 1
? ? ?
 
For infinitely many solutions, 
1 1 1
2 2 2
a b c
a b c
??
 
? 
2
k1
k 1 k 1, –1
1k
? ? ? ? ?
              
...(i) 
 and 
2
3
1k
k 1 k 1
k1
? ? ? ? ?              ...(ii)                  …(ii) 
From (i) and (ii), k = 1 
 
 
 
 
 
[1/2] 
 
[1/2] 
 
[1/2] 
 
[1/2] 
10. 
Since 
p
1,
3
??
??
??
 is the mid-point of the line segment joining the points (2, 0) and 
2
0,
9
??
??
??
 therefore, 
2
0
p1
9
p
3 2 3
?
? ? ?
 
The line 5x + 3y + 2 = 0 passes through the point (–1, 1) as 5(–1) + 3(1) + 2 = 0 
 
 
 
 
[1] 
 
[1] 
11. 
(i) P(square number) = 
8
113
 
(ii) P(multiple of 7) = 
16
113
 
 
[1] 
 
[1] 
 
 
12. Let number of red balls be = x 
? P(red ball) = 
x
12
 
If 6 more red balls are added: 
The number of red balls = x + 6 
P(red ball) = 
x6
18
?
 
Since,  
x 6 x
2 x 3
18 12
? ??
? ? ?
??
??
 
? There are 3 red balls in the bag. 
 
 
 
[1/2] 
 
 
 
[1] 
 
 
[1/2] 
 
Section C 
13. Let n = 3k, 3k + 1 or 3k + 2. 
(i) When n = 3k: 
 n is divisible by 3. 
 n + 2 = 3k + 2 ? n + 2 is not divisible by 3. 
 n + 4 = 3k + 4 = 3(k + 1) + 1 ? n + 4 is not divisible by 3. 
(ii) When n = 3k + 1: 
 n is not divisible by 3. 
 n + 2 = (3k + 1) + 2 = 3k + 3 = 3(k + 1) ?  n + 2 is divisible by 3. 
 n + 4 = (3k + 1) + 4 = 3k + 5 = 3(k + 1) + 2 ? n + 4 is not divisible by 3. 
(iii) When n = 3k + 2: 
 n is not divisible by 3. 
 n + 2 = (3k + 2) + 2 = 3k + 4 = 3(k + 1) + 1 ? n + 2 is not divisible by 3. 
 n + 4 = (3k + 2) + 4 = 3k + 6 = 3(k + 2) ? n + 4 is divisible by 3. 
 Hence exactly one of the numbers n, n + 2 or n + 4 is divisible by 3. 
 
 
 
 
[1] 
 
 
 
[1] 
 
 
 
 
[1] 
14. 
Since 
55
and
33
? are the two zeroes therefore, 
2
5 5 1
x x (3x 5)
3 3 3
? ? ? ?
? ? ? ?
? ? ? ?
? ? ? ?
? ? ? ?
 
is a factor of given polynomial. 
We divide the given polynomial by 3x
2
 – 5. 
                                                     x
2
 + 2x + 1 
               
For other zeroes, x
2
 + 2x + 1 = 0 ? (x + 1)
2
 = 0, x = –1, –1  
? Zeroes of the given polynomial are 
55
, , –1and –1
33
? . 
 
[1] 
 
 
 
 
 
 
 
 
 [1] 
 
 
 
 
 
 
 
 [1] 
 
 
15. Let the ten’s and the units digit be y and x respectively. 
So, the number is 10y + x. 
The number when digits are reversed is 10x + y. 
Now, 7(10y + x) = 4(10x + y) ? 2y = x             …(i)  
Also x – y = 3                                                      …(ii) 
Solving (1) and (2), we get y = 3 and x = 6. 
Hence the number is 36. 
 
[1/2] 
[1/2] 
[1] 
[1/2] 
 
[1/2] 
16. Let x-axis divides the line segment joining (–4, –6) and (–1, 7) at the point P in the 
ratio 1 : k. 
Now, coordinates of point of division 
–1– 4k 7 – 6k
P,
k 1 k 1
??
??
??
??
 
Since P lies on x-axis, therefore 
7 6k
0
k1
?
?
?
 
                                                        
? 7 – 6k = 0 
                                                        
?  k = 
7
6
 
Hence the ratio is 
7
1: 6 : 7
6
?  
Now, the coordinates of  P are 
34
,0
13
???
??
??
. 
OR 
Let the height of parallelogram taking AB as base be h. 
Now AB = 
2 2 2 2
(7 4) (2 2) 3 4 5 units ? ? ? ? ? ? . 
Area ( ? ABC) = ? ?
1 49
4(2 – 9) 7(9 2) 0(–2 – 2) sq units
22
? ? ? ? . 
Now,  
1 49
AB h
22
? ? ? ? 
 
? 
1 49
5h
22
? ? ? ? 
? ?h = 
49
9.8 units
5
? . 
 
[1/2] 
 
 
 
[1] 
 
 
 
 
[1/2] 
 
[1] 
 
 
 
 
[1] 
 
[1] 
 
 
 
 
 
 
[1] 
17. ? SQN = ? TRM    (CPCT as NSQ MTR) ? ? ? 
 
Since, P 1 2 ? ? ? ? ? = P PQR PRQ ? ? ? ? ?    (Angle sum property) 
? 12 ? ? ? = PQR PRQ ? ? ? 
? 2 1 2 PQR ? ? ?  (as 1 2 and PQR PRQ) ? ? ? ? ? ? ? ?  
1 ? = PQR ? 
[1] 
 
 
 
 
 
 
 
 
 
 
 [1] 
 
 
 
Also 2 ? = PRQ ? 
And SPT ? = QPR ?  (common) 
PTS ~ PRQ ??      (By AAA similarity criterion)  
 
OR 
                              
 
Construction: Draw AP BC ? 
In 
2 2 2
ADP, AD AP DP ? ? ? 
2 2 2
AD AP (BP BD) ? ? ? 
2 2 2 2
AD AP BP BD 2(BP)(BD) ? ? ? ? 
2
22
1 BC BC
AD AB BC 2
3 2 3
? ? ? ? ? ?
? ? ?
?? ? ? ? ?
?? ? ? ? ?
 
? ?
22
7
AD AB BC AB
9
?? 
22
9AD 7AB ? 
 
 
[1] 
 
 
 
 
 
 
 
 
 
 
 
[1/2] 
 
 [1/2] 
 
[1/2] 
 
 
 
[1] 
 
 
 
[1/2] 
18. Join OC 
In ? OPA and ? OCA 
OP = OC    (radii of same circle) 
PA = CA (length of two tangents) 
 
AO = AO (Common) 
? ? OPA ? ? OCA (By SSS congruency criterion) 
Hence, ? 1 = ? 2   (CPCT) 
Similarly ? 3 = ? 4 
Now, ? PAB + ? QBA = 180° 
? 2 ? 2 + 2 ? 4 = 180° 
? ? 2 + ? 4 = 90° 
? ? AOB = 90°   (Angle sum property)  
 
 
 
 
 
 
 
 
 
 
 
 
 
[1] 
 
 
[1] 
 
 
[1] 
Page 5


 
 
Marking Scheme  
Mathematics Class X (2017-18) 
Section A 
S.No. Answer Marks 
1. Non terminating repeating decimal expansion.  [1] 
2. k = ±4 [1] 
3. a
11
 = –25 [1] 
4. (0, 5) [1] 
5. 9 : 49 [1] 
6. 25 [1] 
 
Section B 
7. LCM (p, q) = a
3
b
3
  
HCF (p, q) = a
2
b 
LCM (p, q) × HCF (p, q) = a
5
b
4
 = (a
2
b
3
) (a
3
 b) = pq 
[1/2] 
[1/2] 
[1] 
8. S
n
 = 2n
2
 + 3n 
S
1
 = 5 = a
1 
S
2
 = a
1
 + a
2
 = 14 ? a
2
 = 9 
d = a
2
 – a
1
= 4 
a
16
 = a
1
 + 15d = 5 + 15(4) = 65 
[1/2] 
[1/2] 
[1/2] 
 
[1/2] 
9. For pair of equations kx + 1y = k
2
 and 1x + ky = 1 
We have:  
2
1 1 1
2 2 2
a k b 1 c k
,,
a 1 b k c 1
? ? ?
 
For infinitely many solutions, 
1 1 1
2 2 2
a b c
a b c
??
 
? 
2
k1
k 1 k 1, –1
1k
? ? ? ? ?
              
...(i) 
 and 
2
3
1k
k 1 k 1
k1
? ? ? ? ?              ...(ii)                  …(ii) 
From (i) and (ii), k = 1 
 
 
 
 
 
[1/2] 
 
[1/2] 
 
[1/2] 
 
[1/2] 
10. 
Since 
p
1,
3
??
??
??
 is the mid-point of the line segment joining the points (2, 0) and 
2
0,
9
??
??
??
 therefore, 
2
0
p1
9
p
3 2 3
?
? ? ?
 
The line 5x + 3y + 2 = 0 passes through the point (–1, 1) as 5(–1) + 3(1) + 2 = 0 
 
 
 
 
[1] 
 
[1] 
11. 
(i) P(square number) = 
8
113
 
(ii) P(multiple of 7) = 
16
113
 
 
[1] 
 
[1] 
 
 
12. Let number of red balls be = x 
? P(red ball) = 
x
12
 
If 6 more red balls are added: 
The number of red balls = x + 6 
P(red ball) = 
x6
18
?
 
Since,  
x 6 x
2 x 3
18 12
? ??
? ? ?
??
??
 
? There are 3 red balls in the bag. 
 
 
 
[1/2] 
 
 
 
[1] 
 
 
[1/2] 
 
Section C 
13. Let n = 3k, 3k + 1 or 3k + 2. 
(i) When n = 3k: 
 n is divisible by 3. 
 n + 2 = 3k + 2 ? n + 2 is not divisible by 3. 
 n + 4 = 3k + 4 = 3(k + 1) + 1 ? n + 4 is not divisible by 3. 
(ii) When n = 3k + 1: 
 n is not divisible by 3. 
 n + 2 = (3k + 1) + 2 = 3k + 3 = 3(k + 1) ?  n + 2 is divisible by 3. 
 n + 4 = (3k + 1) + 4 = 3k + 5 = 3(k + 1) + 2 ? n + 4 is not divisible by 3. 
(iii) When n = 3k + 2: 
 n is not divisible by 3. 
 n + 2 = (3k + 2) + 2 = 3k + 4 = 3(k + 1) + 1 ? n + 2 is not divisible by 3. 
 n + 4 = (3k + 2) + 4 = 3k + 6 = 3(k + 2) ? n + 4 is divisible by 3. 
 Hence exactly one of the numbers n, n + 2 or n + 4 is divisible by 3. 
 
 
 
 
[1] 
 
 
 
[1] 
 
 
 
 
[1] 
14. 
Since 
55
and
33
? are the two zeroes therefore, 
2
5 5 1
x x (3x 5)
3 3 3
? ? ? ?
? ? ? ?
? ? ? ?
? ? ? ?
? ? ? ?
 
is a factor of given polynomial. 
We divide the given polynomial by 3x
2
 – 5. 
                                                     x
2
 + 2x + 1 
               
For other zeroes, x
2
 + 2x + 1 = 0 ? (x + 1)
2
 = 0, x = –1, –1  
? Zeroes of the given polynomial are 
55
, , –1and –1
33
? . 
 
[1] 
 
 
 
 
 
 
 
 
 [1] 
 
 
 
 
 
 
 
 [1] 
 
 
15. Let the ten’s and the units digit be y and x respectively. 
So, the number is 10y + x. 
The number when digits are reversed is 10x + y. 
Now, 7(10y + x) = 4(10x + y) ? 2y = x             …(i)  
Also x – y = 3                                                      …(ii) 
Solving (1) and (2), we get y = 3 and x = 6. 
Hence the number is 36. 
 
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[1/2] 
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[1/2] 
16. Let x-axis divides the line segment joining (–4, –6) and (–1, 7) at the point P in the 
ratio 1 : k. 
Now, coordinates of point of division 
–1– 4k 7 – 6k
P,
k 1 k 1
??
??
??
??
 
Since P lies on x-axis, therefore 
7 6k
0
k1
?
?
?
 
                                                        
? 7 – 6k = 0 
                                                        
?  k = 
7
6
 
Hence the ratio is 
7
1: 6 : 7
6
?  
Now, the coordinates of  P are 
34
,0
13
???
??
??
. 
OR 
Let the height of parallelogram taking AB as base be h. 
Now AB = 
2 2 2 2
(7 4) (2 2) 3 4 5 units ? ? ? ? ? ? . 
Area ( ? ABC) = ? ?
1 49
4(2 – 9) 7(9 2) 0(–2 – 2) sq units
22
? ? ? ? . 
Now,  
1 49
AB h
22
? ? ? ? 
 
? 
1 49
5h
22
? ? ? ? 
? ?h = 
49
9.8 units
5
? . 
 
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[1] 
17. ? SQN = ? TRM    (CPCT as NSQ MTR) ? ? ? 
 
Since, P 1 2 ? ? ? ? ? = P PQR PRQ ? ? ? ? ?    (Angle sum property) 
? 12 ? ? ? = PQR PRQ ? ? ? 
? 2 1 2 PQR ? ? ?  (as 1 2 and PQR PRQ) ? ? ? ? ? ? ? ?  
1 ? = PQR ? 
[1] 
 
 
 
 
 
 
 
 
 
 
 [1] 
 
 
 
Also 2 ? = PRQ ? 
And SPT ? = QPR ?  (common) 
PTS ~ PRQ ??      (By AAA similarity criterion)  
 
OR 
                              
 
Construction: Draw AP BC ? 
In 
2 2 2
ADP, AD AP DP ? ? ? 
2 2 2
AD AP (BP BD) ? ? ? 
2 2 2 2
AD AP BP BD 2(BP)(BD) ? ? ? ? 
2
22
1 BC BC
AD AB BC 2
3 2 3
? ? ? ? ? ?
? ? ?
?? ? ? ? ?
?? ? ? ? ?
 
? ?
22
7
AD AB BC AB
9
?? 
22
9AD 7AB ? 
 
 
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[1/2] 
18. Join OC 
In ? OPA and ? OCA 
OP = OC    (radii of same circle) 
PA = CA (length of two tangents) 
 
AO = AO (Common) 
? ? OPA ? ? OCA (By SSS congruency criterion) 
Hence, ? 1 = ? 2   (CPCT) 
Similarly ? 3 = ? 4 
Now, ? PAB + ? QBA = 180° 
? 2 ? 2 + 2 ? 4 = 180° 
? ? 2 + ? 4 = 90° 
? ? AOB = 90°   (Angle sum property)  
 
 
 
 
 
 
 
 
 
 
 
 
 
[1] 
 
 
[1] 
 
 
[1] 
 
 
19. 
2 2 2
2 2 2 2
cosec 63 tan 24 sin 63 cos63 sin 27 sin 27 sec63
cot 66 sec 27 2(cosec 65 tan 25 )
? ? ? ? ? ? ? ? ? ? ? ?
?
? ? ? ? ? ?
 
= 
2 2 2
2 2 2 2
cosec 63 tan 24 sin 63 cos63 cos(90 – 27 ) sin 27 cosec(90 – 63 )
tan (90 66 ) cosec (90 27 ) 2[cosec 65 cot (90 – 25 )]
? ? ? ? ? ? ? ? ? ? ? ? ? ?
?
? ? ? ? ? ? ? ? ? ? ?
 
= 
2 2 2 2
2 2 2 2
cosec 63 tan 24 sin 63 cos 63 sin 27 cosec27°
tan 24 cosec 63 2(cosec 65 – cot 65 )
? ? ? ? ? ? ? ?
?
? ? ? ? ?
 
= 
11
12
2(1)
?
?? 
OR 
sin cos 2 ? ? ? ? 
? 
? ?
2
2
(sin cos ) 2 ? ? ? ? 
? 
22
sin cos 2sin cos 2 ? ? ? ? ? ? ? 
? 1 2sin cos 2 ? ? ? ? 
? 
1
sin cos
2
? ? ?                         ...(i) 
we know, 
22
sin cos 1 ? ? ? ?    ....(ii) 
Dividing (ii) by (i) we get 
22
sin cos 1
sin cos 1/2
? ? ?
?
??
 
? tan cot 2 ? ? ? ? 
 
 
 
[1] 
 
 
[1] 
 
[1] 
 
 
 
 
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[1] 
 
[1/2] 
 
 
 
 
[1] 
20. We know,  AC = r 
In ? ACB, ?BC
2
 = AC
2
 + AB
2
 
? BC = AC 2
  
( AB AC) ? 
? BC = r2 
 
 
Required area = ar( ? ACB) + ar(semicircle on BC as diameter) –ar(quadrant 
ABPC) 
= 
2
2
1 1 r 2 1
r r r
2 2 2 4
??
? ? ? ? ? ? ? ?
??
??
 
= 
2 2 2
r r r
–
2 4 4
??
? 
= 
2
22
r 196
cm 98 cm
22
?? 
 
 
 
[1] 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
[1] 
 
 
 
[1] 
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