Class 8 Exam  >  Class 8 Notes  >  Mathematics (Maths) Class 8  >  NCERT Solutions: Factorisation (Exercise 12.1, 12.2, 12.3)

Factorisation (Exercise 12.1, 12.2, 12.3) NCERT Solutions | Mathematics (Maths) Class 8 PDF Download

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 Page 1


 
 
    
 
 
 
 
  
 
Exercise 2 1 .1 
 
1. Find the common factors of the terms 
 
i. 12x,36 
Ans:  
Write the factors of each term separately: 
12x 2 2 3 x ? ? ? ? 
36 2 2 3 3 ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,2,3.  
Multiply the common factors, 2 2 3 12 ? ? ? 
 
ii.2y,22xy 
Ans:  
Write the factors of each term separately: 
2y 2 y ?? 
22xy 2 11 x y ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2, y .  
Multiply the common factors, 2 y 2y ?? .  
 
iii.
22
14pq,28p q 
Ans:  
Write the factors of each term separately: 
14pq 2 7 p q ? ? ? ? 
22
28p q 2 2 7 p p q q ? ? ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,7,p,q .  
Multiply the common factors, 2 7 p q 14pq ? ? ? ? .  
 
iv.
2
2x,3x ,4 
Ans:  
Page 2


 
 
    
 
 
 
 
  
 
Exercise 2 1 .1 
 
1. Find the common factors of the terms 
 
i. 12x,36 
Ans:  
Write the factors of each term separately: 
12x 2 2 3 x ? ? ? ? 
36 2 2 3 3 ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,2,3.  
Multiply the common factors, 2 2 3 12 ? ? ? 
 
ii.2y,22xy 
Ans:  
Write the factors of each term separately: 
2y 2 y ?? 
22xy 2 11 x y ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2, y .  
Multiply the common factors, 2 y 2y ?? .  
 
iii.
22
14pq,28p q 
Ans:  
Write the factors of each term separately: 
14pq 2 7 p q ? ? ? ? 
22
28p q 2 2 7 p p q q ? ? ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,7,p,q .  
Multiply the common factors, 2 7 p q 14pq ? ? ? ? .  
 
iv.
2
2x,3x ,4 
Ans:  
 
 
    
 
 
Write the factors of each term separately: 
2x 2 x ?? 
2
3x 3 x x ? ? ? 
4 2 2 ?? 
The factors that appear in both the lists are the common factors.  
Hence, the common factor is 1.  
 
v.
22
6abc,24ab ,12a b 
Ans:  
Write the factors of each term separately: 
6abc 2 3 a b c ? ? ? ? ? 
2
24ab 2 2 2 3 a b b ? ? ? ? ? ? ? 
2
12a b 2 2 3 a a b ? ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,3,a,b .  
Multiply the common factors, 2 3 a b 6ab ? ? ? ? .  
 
vi.
32
16x , 4x ,32x ? 
Ans:  
Write the factors of each term separately: 
3
16x 2 2 2 2 x x x ? ? ? ? ? ? ? 
2
4x 1 2 2 x x ? ? ? ? ? ? ? 
32x 2 2 2 2 2 x ? ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,2,x  
Multiply the common factors, 2 2 x 4x ? ? ? 
 
vii.10pq,20qr,30rp 
Ans:  
Write the factors of each term separately: 
10pq 2 5 p q ? ? ? ? 
20qr 2 2 5 q r ? ? ? ? ? 
30rp 2 3 5 r p ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,5 . 
Multiply the common factors, 2 5 10 ?? .  
 
viii.
2 3 3 2 2 2
3x y ,10x y ,6x y z 
Ans:  
Page 3


 
 
    
 
 
 
 
  
 
Exercise 2 1 .1 
 
1. Find the common factors of the terms 
 
i. 12x,36 
Ans:  
Write the factors of each term separately: 
12x 2 2 3 x ? ? ? ? 
36 2 2 3 3 ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,2,3.  
Multiply the common factors, 2 2 3 12 ? ? ? 
 
ii.2y,22xy 
Ans:  
Write the factors of each term separately: 
2y 2 y ?? 
22xy 2 11 x y ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2, y .  
Multiply the common factors, 2 y 2y ?? .  
 
iii.
22
14pq,28p q 
Ans:  
Write the factors of each term separately: 
14pq 2 7 p q ? ? ? ? 
22
28p q 2 2 7 p p q q ? ? ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,7,p,q .  
Multiply the common factors, 2 7 p q 14pq ? ? ? ? .  
 
iv.
2
2x,3x ,4 
Ans:  
 
 
    
 
 
Write the factors of each term separately: 
2x 2 x ?? 
2
3x 3 x x ? ? ? 
4 2 2 ?? 
The factors that appear in both the lists are the common factors.  
Hence, the common factor is 1.  
 
v.
22
6abc,24ab ,12a b 
Ans:  
Write the factors of each term separately: 
6abc 2 3 a b c ? ? ? ? ? 
2
24ab 2 2 2 3 a b b ? ? ? ? ? ? ? 
2
12a b 2 2 3 a a b ? ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,3,a,b .  
Multiply the common factors, 2 3 a b 6ab ? ? ? ? .  
 
vi.
32
16x , 4x ,32x ? 
Ans:  
Write the factors of each term separately: 
3
16x 2 2 2 2 x x x ? ? ? ? ? ? ? 
2
4x 1 2 2 x x ? ? ? ? ? ? ? 
32x 2 2 2 2 2 x ? ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,2,x  
Multiply the common factors, 2 2 x 4x ? ? ? 
 
vii.10pq,20qr,30rp 
Ans:  
Write the factors of each term separately: 
10pq 2 5 p q ? ? ? ? 
20qr 2 2 5 q r ? ? ? ? ? 
30rp 2 3 5 r p ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,5 . 
Multiply the common factors, 2 5 10 ?? .  
 
viii.
2 3 3 2 2 2
3x y ,10x y ,6x y z 
Ans:  
 
 
    
 
 
Write the factors of each term separately: 
23
3x y 3 x x y y y ? ? ? ? ? ? 
32
10x y 2 5 x x x y y ? ? ? ? ? ? ? 
22
6x y z 2 3 x x y y z ? ? ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2 7 p q 14pq ? ? ? ? .  
 
2. Factorise the following expressions 
 
i. 7x 42 ? 
Ans:  
Take out the common factors from all the terms to factorize.  
 7x 7 x ?? 
42 2 3 7 ? ? ? 
The common factor is 7 
7x 42 (7 x) (2 3 7) 7(x 6) ? ? ? ? ? ? ? ? ? 
 
ii. 6p 12q ? 
Ans:  
Take out the common factors from all the terms to factorize.  
6p 2 3 p ? ? ? 
12q 2 2 3 q ? ? ? ? 
The common factors are 2 and 3. 
6p 12q (2 3 p) (2 2 3 q) ? ? ? ? ? ? ? ? 
2 3[p (2 q)] ? ? ? ? 
6(p 2q) ?? 
 
iii. 
2
7a 14a ? 
Ans:  
Take out the common factors from all the terms to factorize.  
2
7a 7 a a ? ? ? 
14a 2 7 a ? ? ? 
The common factors are 7 and a 
2
7a 14a (7 a a) (2 7 a) ? ? ? ? ? ? ? ? 
7 a[a 2] ? ? ? 
7a(a 2) ?? 
 
iv. 
3
16z 20z ?? 
Ans:  
Page 4


 
 
    
 
 
 
 
  
 
Exercise 2 1 .1 
 
1. Find the common factors of the terms 
 
i. 12x,36 
Ans:  
Write the factors of each term separately: 
12x 2 2 3 x ? ? ? ? 
36 2 2 3 3 ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,2,3.  
Multiply the common factors, 2 2 3 12 ? ? ? 
 
ii.2y,22xy 
Ans:  
Write the factors of each term separately: 
2y 2 y ?? 
22xy 2 11 x y ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2, y .  
Multiply the common factors, 2 y 2y ?? .  
 
iii.
22
14pq,28p q 
Ans:  
Write the factors of each term separately: 
14pq 2 7 p q ? ? ? ? 
22
28p q 2 2 7 p p q q ? ? ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,7,p,q .  
Multiply the common factors, 2 7 p q 14pq ? ? ? ? .  
 
iv.
2
2x,3x ,4 
Ans:  
 
 
    
 
 
Write the factors of each term separately: 
2x 2 x ?? 
2
3x 3 x x ? ? ? 
4 2 2 ?? 
The factors that appear in both the lists are the common factors.  
Hence, the common factor is 1.  
 
v.
22
6abc,24ab ,12a b 
Ans:  
Write the factors of each term separately: 
6abc 2 3 a b c ? ? ? ? ? 
2
24ab 2 2 2 3 a b b ? ? ? ? ? ? ? 
2
12a b 2 2 3 a a b ? ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,3,a,b .  
Multiply the common factors, 2 3 a b 6ab ? ? ? ? .  
 
vi.
32
16x , 4x ,32x ? 
Ans:  
Write the factors of each term separately: 
3
16x 2 2 2 2 x x x ? ? ? ? ? ? ? 
2
4x 1 2 2 x x ? ? ? ? ? ? ? 
32x 2 2 2 2 2 x ? ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,2,x  
Multiply the common factors, 2 2 x 4x ? ? ? 
 
vii.10pq,20qr,30rp 
Ans:  
Write the factors of each term separately: 
10pq 2 5 p q ? ? ? ? 
20qr 2 2 5 q r ? ? ? ? ? 
30rp 2 3 5 r p ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,5 . 
Multiply the common factors, 2 5 10 ?? .  
 
viii.
2 3 3 2 2 2
3x y ,10x y ,6x y z 
Ans:  
 
 
    
 
 
Write the factors of each term separately: 
23
3x y 3 x x y y y ? ? ? ? ? ? 
32
10x y 2 5 x x x y y ? ? ? ? ? ? ? 
22
6x y z 2 3 x x y y z ? ? ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2 7 p q 14pq ? ? ? ? .  
 
2. Factorise the following expressions 
 
i. 7x 42 ? 
Ans:  
Take out the common factors from all the terms to factorize.  
 7x 7 x ?? 
42 2 3 7 ? ? ? 
The common factor is 7 
7x 42 (7 x) (2 3 7) 7(x 6) ? ? ? ? ? ? ? ? ? 
 
ii. 6p 12q ? 
Ans:  
Take out the common factors from all the terms to factorize.  
6p 2 3 p ? ? ? 
12q 2 2 3 q ? ? ? ? 
The common factors are 2 and 3. 
6p 12q (2 3 p) (2 2 3 q) ? ? ? ? ? ? ? ? 
2 3[p (2 q)] ? ? ? ? 
6(p 2q) ?? 
 
iii. 
2
7a 14a ? 
Ans:  
Take out the common factors from all the terms to factorize.  
2
7a 7 a a ? ? ? 
14a 2 7 a ? ? ? 
The common factors are 7 and a 
2
7a 14a (7 a a) (2 7 a) ? ? ? ? ? ? ? ? 
7 a[a 2] ? ? ? 
7a(a 2) ?? 
 
iv. 
3
16z 20z ?? 
Ans:  
 
 
    
 
 
Take out the common factors from all the terms to factorize.  
 16z 2 2 2 2 z ? ? ? ? ? 
3
20z 2 2 5 z z z ? ? ? ? ? ? 
The common factors are 2,2, and z . 
3
16z 20z (2 2 2 2 z) (2 2 5 z z z) ? ? ? ? ? ? ? ? ? ? ? ? ? ? 
(2 2 z)[ (2 2) (5 z z)] ? ? ? ? ? ? ? ? 
? ?
2
4z 4 5z ? ? ? 
 
v. 
2
20l m 30alm ? 
Ans:  
Take out the common factors from all the terms to factorize.  
2
20l m 2 2 5 1 1 m ? ? ? ? ? ? 
30alm 2 3 5 a 1 m ? ? ? ? ? ? 
The common factors are 2,5,1, and m . 
2
20l m 30alm (2 2 5 1 1 m) (2 3 5 a 1 m) ? ? ? ? ? ? ? ? ? ? ? ? ? ? 
(2 5 1 m)[(2 l) (3 a)] ? ? ? ? ? ? ? 
10lm(2l 3a) ?? 
 
vi. 
22
5x y 15xy ? 
Ans:  
Take out the common factors from all the terms to factorize.  
2
5x y 5 x x y ? ? ? ? 
2
15xy 3 5 x y y ? ? ? ? ? 
The common factors are5,x , and y. 
22
5x y 15xy (5 x x y) (3 5 x y y) ? ? ? ? ? ? ? ? ? ? 
5 x y[x (3 y)] ? ? ? ? ? 
5xy(x 3y) ?? 
 
vii. 
2 2 2
10a 15b 20c ?? 
Ans:  
Take out the common factors from all the terms to factorize.  
2
10a 2 5 a a ? ? ? ? 
2
15b 3 5 b b ? ? ? ? 
2
20c 2 2 5 c c ? ? ? ? ? 
The common factor is 5 
2 2 2
10a 15b 20c (2 5 a a) (3 5 b b) (2 2 5 c c) ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 
5[(2 a a) (3 b b) (2 2 c c)] ? ? ? ? ? ? ? ? ? ? 
Page 5


 
 
    
 
 
 
 
  
 
Exercise 2 1 .1 
 
1. Find the common factors of the terms 
 
i. 12x,36 
Ans:  
Write the factors of each term separately: 
12x 2 2 3 x ? ? ? ? 
36 2 2 3 3 ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,2,3.  
Multiply the common factors, 2 2 3 12 ? ? ? 
 
ii.2y,22xy 
Ans:  
Write the factors of each term separately: 
2y 2 y ?? 
22xy 2 11 x y ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2, y .  
Multiply the common factors, 2 y 2y ?? .  
 
iii.
22
14pq,28p q 
Ans:  
Write the factors of each term separately: 
14pq 2 7 p q ? ? ? ? 
22
28p q 2 2 7 p p q q ? ? ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,7,p,q .  
Multiply the common factors, 2 7 p q 14pq ? ? ? ? .  
 
iv.
2
2x,3x ,4 
Ans:  
 
 
    
 
 
Write the factors of each term separately: 
2x 2 x ?? 
2
3x 3 x x ? ? ? 
4 2 2 ?? 
The factors that appear in both the lists are the common factors.  
Hence, the common factor is 1.  
 
v.
22
6abc,24ab ,12a b 
Ans:  
Write the factors of each term separately: 
6abc 2 3 a b c ? ? ? ? ? 
2
24ab 2 2 2 3 a b b ? ? ? ? ? ? ? 
2
12a b 2 2 3 a a b ? ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,3,a,b .  
Multiply the common factors, 2 3 a b 6ab ? ? ? ? .  
 
vi.
32
16x , 4x ,32x ? 
Ans:  
Write the factors of each term separately: 
3
16x 2 2 2 2 x x x ? ? ? ? ? ? ? 
2
4x 1 2 2 x x ? ? ? ? ? ? ? 
32x 2 2 2 2 2 x ? ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,2,x  
Multiply the common factors, 2 2 x 4x ? ? ? 
 
vii.10pq,20qr,30rp 
Ans:  
Write the factors of each term separately: 
10pq 2 5 p q ? ? ? ? 
20qr 2 2 5 q r ? ? ? ? ? 
30rp 2 3 5 r p ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2,5 . 
Multiply the common factors, 2 5 10 ?? .  
 
viii.
2 3 3 2 2 2
3x y ,10x y ,6x y z 
Ans:  
 
 
    
 
 
Write the factors of each term separately: 
23
3x y 3 x x y y y ? ? ? ? ? ? 
32
10x y 2 5 x x x y y ? ? ? ? ? ? ? 
22
6x y z 2 3 x x y y z ? ? ? ? ? ? ? 
The factors that appear in both the lists are the common factors.  
Hence, the common factors are 2 7 p q 14pq ? ? ? ? .  
 
2. Factorise the following expressions 
 
i. 7x 42 ? 
Ans:  
Take out the common factors from all the terms to factorize.  
 7x 7 x ?? 
42 2 3 7 ? ? ? 
The common factor is 7 
7x 42 (7 x) (2 3 7) 7(x 6) ? ? ? ? ? ? ? ? ? 
 
ii. 6p 12q ? 
Ans:  
Take out the common factors from all the terms to factorize.  
6p 2 3 p ? ? ? 
12q 2 2 3 q ? ? ? ? 
The common factors are 2 and 3. 
6p 12q (2 3 p) (2 2 3 q) ? ? ? ? ? ? ? ? 
2 3[p (2 q)] ? ? ? ? 
6(p 2q) ?? 
 
iii. 
2
7a 14a ? 
Ans:  
Take out the common factors from all the terms to factorize.  
2
7a 7 a a ? ? ? 
14a 2 7 a ? ? ? 
The common factors are 7 and a 
2
7a 14a (7 a a) (2 7 a) ? ? ? ? ? ? ? ? 
7 a[a 2] ? ? ? 
7a(a 2) ?? 
 
iv. 
3
16z 20z ?? 
Ans:  
 
 
    
 
 
Take out the common factors from all the terms to factorize.  
 16z 2 2 2 2 z ? ? ? ? ? 
3
20z 2 2 5 z z z ? ? ? ? ? ? 
The common factors are 2,2, and z . 
3
16z 20z (2 2 2 2 z) (2 2 5 z z z) ? ? ? ? ? ? ? ? ? ? ? ? ? ? 
(2 2 z)[ (2 2) (5 z z)] ? ? ? ? ? ? ? ? 
? ?
2
4z 4 5z ? ? ? 
 
v. 
2
20l m 30alm ? 
Ans:  
Take out the common factors from all the terms to factorize.  
2
20l m 2 2 5 1 1 m ? ? ? ? ? ? 
30alm 2 3 5 a 1 m ? ? ? ? ? ? 
The common factors are 2,5,1, and m . 
2
20l m 30alm (2 2 5 1 1 m) (2 3 5 a 1 m) ? ? ? ? ? ? ? ? ? ? ? ? ? ? 
(2 5 1 m)[(2 l) (3 a)] ? ? ? ? ? ? ? 
10lm(2l 3a) ?? 
 
vi. 
22
5x y 15xy ? 
Ans:  
Take out the common factors from all the terms to factorize.  
2
5x y 5 x x y ? ? ? ? 
2
15xy 3 5 x y y ? ? ? ? ? 
The common factors are5,x , and y. 
22
5x y 15xy (5 x x y) (3 5 x y y) ? ? ? ? ? ? ? ? ? ? 
5 x y[x (3 y)] ? ? ? ? ? 
5xy(x 3y) ?? 
 
vii. 
2 2 2
10a 15b 20c ?? 
Ans:  
Take out the common factors from all the terms to factorize.  
2
10a 2 5 a a ? ? ? ? 
2
15b 3 5 b b ? ? ? ? 
2
20c 2 2 5 c c ? ? ? ? ? 
The common factor is 5 
2 2 2
10a 15b 20c (2 5 a a) (3 5 b b) (2 2 5 c c) ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 
5[(2 a a) (3 b b) (2 2 c c)] ? ? ? ? ? ? ? ? ? ? 
 
 
    
 
 
? ?
222
5 2a 3b 4c ? ? ? 
 
viii. 
2
4a 4ab 4ca ? ? ? 
Ans:  
Take out the common factors from all the terms to factorize.  
2
4a 2 2 a a ? ? ? ? 
4ab 2 2 a b ? ? ? ? 
4ca 2 2 c a ? ? ? ? 
The common factors are 2,2, and a 
2
4a 4ab 4ca (2 2 a a) (2 2 a b) (2 2 c a) ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 
2 2 a[ (a) b c] ? ? ? ? ? ? 
4a( a b c) ? ? ? ? 
 
ix. 
2 2 2
x yz xy z xyz ?? 
Ans:  
Take out the common factors from all the terms to factorize.  
2
x yz x x y z ? ? ? ? 
2
xy z x y y z ? ? ? ? 
2
xyz x y z z ? ? ? ? 
The common factors are x,y , and z 
2 2 2
x yz xy z xyz (x x y z) (x y y z) (x y z z) ? ? ? ? ? ? ? ? ? ? ? ? ? ? 
x y z[x y z] ? ? ? ? ? 
xyz(x y z) ? ? ? 
 
x. 
22
ax y bxy cxyz ?? 
Ans:  
Take out the common factors from all the terms to factorize.  
2
ax y a x x y ? ? ? ? 
2
bxy b x y y ? ? ? ? 
cxyz c x y z ? ? ? ? 
The common factors are x and y. 
22
ax y bxy cxyz (a x x y) (b x y y) (c x y z) ? ? ? ? ? ? ? ? ? ? ? ? ? ? 
(x y)[(a x) (b y) (c z)] ? ? ? ? ? ? ? 
xy(ax by cz) ? ? ? 
 
3. Factorise 
 
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