Question

A is 25% older than B. By what percent is B younger than A?

Answer 1

Alternative Method:
Let age of B = 100 years
∴ Age of A
= 100 + 100 x `(25)/(100)`
= 125 years
Difference in age by which A is older than B 
= 125 - 100
= 25 years
∴ % by which B is younger than A
= `(25)/(125) xx 100`
= 20%