Question

A sum of money double itself in 10 years. Find the rate of interest.

Answer 1

Let the sum of money ,P = x

time, t = 10 yrs

As it get doubled so Amount, A = 2x

Hence interest= A - P = 2x - x = x

Let r be the rate of interest

Now, As Interest = ( P × r × t )/100

so, x = ( x × r × 10 )/100

or, 1 = 10 r / 100

so, r = 10 %

Hence rate of interest is 10 % per annum.