Set up equations and solve them to find the unknown numbers in the following cases:
a) Add 4 to eight times a number; you get 60.
b) One-fifth of a number minus 4 gives 3.
c) If I take three-fourths of a number and add 3 to it, I get 21.
d) When I subtracted 11 from twice a number, the result was 15.
e) Munna subtracts thrice the number of notebooks he has from 50, he finds the result to be 8.
f) Ibenhal thinks of a number. If she adds 19 to it and divides the sum by 5, she will get 8.
g) Anwar thinks of a number. If he takes away 7 from 5/2 of the number, the result is 23.

Solution:

We use the concepts of simple linear equations and fundamental operations like addition, subtraction, multiplication, and division to solve the problem.

(a) Let the number be x.

According to the question,

8x + 4 = 60

8x = 60 – 4

8x = 56

x = 56/8

x = 7

(b) Let the number be y.

According to question,

y/5 − 4 = 3

y/5 = 3 + 4

y/5 = 7

y = 35

(c) Let the number be x.

According to question,

3x/4 + 3 = 21

3x/4 = 21 − 3

3x/4 =18

x =18 × 4/3

x = 24

(d) Let the number be x.

According to question,

2x – 11 = 15

2x = 15 + 11

2x = 26

x = 26/2

x = 13

(e) Let the number be x.

According to question,

50 – 3x = 8

- 3x = 8 - 50

- 3x = - 42

x = - 42/(-3) = 14

(f) Let the number be z.

According to question,

(z +19)/5 = 8

z + 19 = 40

z = 40 – 19 = 21

(g) Let the number be x.

According to question,

5x/2 – 7 = 23

5x/2 = 23 + 7

5x/2 = 30

x = 30 × 2/5

x = 12

☛ Check: NCERT Solutions for Class 7 Maths Chapter 4

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Video Solution:

Set up equations and solve them to find the unknown numbers in the following cases: a) Add 4 to eight times a number; you get 60. b) One-fifth of a number minus 4 gives 3. c) If I take three-fourths of a number and add 3 to it, I get 21. d) When I subtracted 11 from twice a number, the result was 15. e) Munna subtracts thrice the number of notebooks he has from 50, he finds the result to be 8. f) Ibenhal thinks of a number. If she adds 19 to it and divides the sum by 5, she will get 8. g) Anwar thinks of a number. If he takes away 7 from 5/2 of the number, the result is 23.

NCERT Solutions for Class 7 Maths Chapter 4 Exercise 4.4 Question 1

Summary:

The equations for the following case a) Add 4 to eight times a number; you get 60. b) One-fifth of a number minus 4 gives 3. c) If I take three-fourths of a number and add 3 to it, I get 21. d) When I subtracted 11 from twice a number, the result was 15. e) Munna subtracts thrice the number of notebooks he has from 50, he finds the result to be 8. f) Ibenhal thinks of a number. If she adds 19 to it and divides the sum by 5, she will get 8. g) Anwar thinks of a number. If he takes away 7 from 5/2 of the number, the result is 23 are (a) x = 7 , (b) y = 35 , (c) x = 24 , (d) x = 13 , (e) x = 14 , (f) z = 21 and (g) x = 12

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