Question

a boy spends 3/4 of his pocket money and then 4/5 of the remainder is given to his sister if he has rupees 40 left what did he have first?

Answer 1

let pocket money be = x
X -3/4x is amount remaining with him after spending money.
X -3/4x= x/4 (on solving)
now he gave 4/5of remaining amount to his sister.
= x/4 - 4/5 of x/4
= x/4 - x/5
= x/20
amount remaining with him is =40
x/20=40
x=800
his pocket money is 800

Answer 2

Answer:

At the start he had 800 rupees.

Solution:

let the boy had x rupees at the start,

he spend 3/4 , left amount = x-3/4x

                                             =x/4

he gave  4/5 of the remainder to sister, so left amount =x/4 - 4/5(x/4)

                                                                                           =x/20

left amount = 40, therefore x/20 = 40

therefore x=800 rupees.