Question

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 note books 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 \(\frac{5}{2}\) of the number, the result is 23.

Answer 1

(a) Let the unknown number be’x’

8 times a number be 8x

According to the question

8x + 4 = 60

8x = 60 – 4

8x = 56

∴ The unknown number x be 7

(b) Let the unknown number be x

Then according to the question

(c) Let the unknown number be x

According to the question

∴ That unknown number be 24.

(d) Let the unknown number be x 

According to the question

2x – 11 = 15

2x = 15 + 11

2x = 26

∴ That unknown number be 13.

(e) Let the unknown number be x

According to the question

50 – 3x = 8

– 3x = 8 – 50

Therefore that unknown number be 14.

(f) Let the unknown number be x

According to the question

∴ That unknown number be 21

(g) Let the unknown number be x

According to the question

That unknown number be 12