# NCERT solution class 7 chapter 4 simple equations exercise 4.2 mathematics

## EXERCISE 4.2

QUESTION 1

Give f‌irst the step you will use to separate the variable and then solve the equation:

(a) x+ 1 = 0

Sol :

Adding 1 to both sides of the given equation, we obtain

x – 1 + 1 = 0 + 1

x = 1

(b) x + 1 = 0

Sol :

Subtracting 1 from both sides of the given equation , we obtain

x + 1 – 1 = 0 – 1

x = – 1

(c) x – 1 = 5

Sol :

Adding 1 to both sides of the given equation, we obtain

x – 1 + 1 = 5 + 1

x = 6

(d) x + 6 = 2

Sol :

Subtracting 6 from both sides of the given equation, we obtain

x + 6 – 6 = 2 – 6

x = – 4

(e) y – 4 = -7

Sol :

adding 4 to both sides of the given equation , we obtain

y – 4 + 4= -7 + 4

y = -3

(f) y – 4 = 4

Sol :

Adding 4 to both sides of the given equation, we obtain

y – 4 + 4 = 4 + 4

y = 8

(g) y + 4 = 4

Sol :

Subtracting 4 from both sides of the given equation , we obtain

y + 4 – 4 = 4 – 4

y = 0

(h) y + 4 = -4

Sol :

Subtracting 4 from both sides of the given equation , we obtain

y + 4 – 4 = 4 – 4

y = -8

QUESTION 2

Give  the f‌irst step you will use to separate the variable and then solve the equation:

(a) 3l = 42

Sol :

Dividing both sides of the given equation by 3, we obtain l = 14

(b) Sol :

Multiplying both sides of the given equation by 2, we obtain b = 12

(c) Sol :

Multiplying both sides of the given equation by 7, we obtain p = 28

(d) 4x = 25

Sol :

Dividing both sides of the given equation by 4, we obtain  (e) 8y = 36

Sol :

Dividing both sides of the given equation by 8, we obtain  (f) Sol :

Multiplying both sides of the given equation by 3, we obtain  (g) Sol :

Multiplying both sides of the given equation by 5, we obtain  (h) 20t = -10

Sol :

Dividing both sides of the given equation by 20, we obtain  QUESTION 3

Give the steps you will use to separate the variable and then solve the equation:

(a) 3n – 2 = 26

Sol :

Adding 2 to both sides of the given equation, we obtain

3n – 2 + 2 = 46 + 2

3n = 48

Dividing both sides of the given equation by 3, we obtain n = 16

(b) 5m + 7 = 7

Sol :

Subtracting 7 from both sides of the given equation, we obtain

5m + 7 – 7 = 17 – 7

5m = 10

Dividing both sides of the given equation by 5, we obtain m = 2

(c) Sol :

Multiplying both sides of the given equation by 3, we obtain 20p = 120

Dividing both sides of the given equation by 20, we obtain p = 6

(d) Sol :

Multiplying both sides of the given equation by 10, we obtain 3p = 60

Dividing both sides of the given equation by 3, we obtain p = 20

QUESTION 4

Solve the following equations:

(a) 10p = 100

Sol : p = 10

(b) 10p + 10

Sol :

10p + 10 – 10 = 100 – 10

10 p = 90 p = 9

(c) Sol : p = 20

(d) Sol : p = -15

(e) Sol : 3p = 24

p = 8

(f) 3s = -9

Sol : x = -3

(g) 3s + 12  = 0

Sol :

3s + 12 -12 = 0 -12

3s = -12 s = -4

(h) 3s = 0

Sol : s = 0

(i) 2q = 6

Sol : q = 3

(j) 2q – 6 = 0

Sol :

2q – 6 + 6 = 0 + 6

2q = 6 q = 3

(k) 2q + 6 = 0

Sol :

2q + 6 – 6 = 0

2q = -6 q = -3

(l) 2q + 6 = 12

Sol :

2q + 6 – 6 = 12 – 6

2q = 6 q = 3

error: Content is protected !! 