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 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 of the number, the result is 23.

Answer 1

(a) Let the number be x.

8 times of this number = 8x

8x + 4 = 60

8x = 60 − 4 (Transposing 4 to R.H.S.)

8x = 56

Dividing both sides by 8,

(b) Let the number be x.

One-fifth of this number =

(Transposing −4 to R.H.S.)

Multiplying both sides by 5,

(c) Let the number be x.

Three-fourth of this number =

(Transposing 3 to R.H.S.)

Multiplying both sides by 4,

Dividing both sides by 3,

(d) Let the number be x.

Twice of this number = 2x

2x − 11 = 15

2x = 15 + 11 (Transposing −11 to R.H.S.)

2x = 26

Dividing both sides by 2,

x = 13

(e) Let the number of books be x.

Thrice the number of books = 3x

50 − 3x = 8

− 3x = 8 −50 (Transposing 50 to R.H.S.)

−3x = −42

Dividing both sides by ­−3,

(f) Let the number be x.

Multiplying both sides by 5,

x + 19 = 40

x = 40 − 19 (Transposing 19 to R.H.S.)

x = 21

(g) Let the number be x.

of this number =

Multiplying both sides by 2,

Dividing both sides by 5,