Question

A number is to be multiplied by the fraction 4/5. but samir, by mistake, multiplied it by 5/4 and obtained the number 81 more than the correct one. what was the original number

Answer 1

let the no. was x

(x)×4/5+81=(x)×5/4

(5x/4)-(4x/5)=81
(25x-16x)/20=81

9x/20=81

x=180

Answer 2

Define x:

Let x be the number

If the number is multiplied by 4/5:

⇒ Number = 4/5 x

If the number is multiplied by 5/4:

⇒ Number = 5/4 x

Solve x:

The difference is 81

5/4 x - 4/5 x = 81

9/20 x = 81

x = 81 ÷ 9/20

x = 81 x 02/9

x = 180

Answer: The number is 180