Question

An amount of money double itself in 10 years. what is the rate of interest ?

Answer 1

Let the principal be x
Time = 10 years
Amount after 10 years gets doubled
So amount = 2x
simple interest = amount - principal
simple interest = 2x - x = x
Rate per annum = SI × 100 / P × T
= x × 100 / x × 10
100x/ 10x = 10
So rate per annum = 10%.