Question

A number is first decreased by 20%. The decreased number is then increased by 20%. The resulting number is less than the original number by 20. Then the original number is ?

Answer 1

Let the original number is x.

If it is decreased by 20%,
20%of x = 20/100 * x = 0.2x
the new number = x - 0.2x = 0.8x

If the new number is increased by 20%,
20%of 0.8x = 20/100 * (0.8x) = 0.16x
the new number = 0.8x + 0.16x = 0.96x

The resulting number is less than original number by 20
So x - 0.96x = 20
⇒ 0.04x = 20
⇒ 4x/100 = 20
⇒ x = 20*100/4 = 500

The number is 500

Answer 2

Let the number be x
therefore, 20% of x = 20/100 * x = x/5
then after decreasing the  no is x - x/5 = 4x/5
then, 20% of 4x/5 = 4x/25
then after increasing the no. is 4x/5 + 4x/25 = 24x/25
A/q
   x - 20 = 24x/25
 x - 24x/25 = 20
x = 500
so, the original no. is 500
I HOPE IT HELPFUL FOR YOU.....