Question

A certain sum of money placed on compound interest amounts to Rs. 4000 in 3 years and Rs. 5000 in 4 years. Calculate the rate of interest.

Answer 1

Sum of money $\to$ II year Rs. 4000 $\to$ III year Rs. 5000
There is increase of Rs. 1000 in 1 year due to interest
$1000=\frac{4000\times R\times 1}{100}$
$\therefore R=25$% per annum.
$[S.I.=\frac{P.R.T}{100}]$