Find the compound interest on Rs. 6,500 for 4 years if the rate of interest is 10% p.a. for the first 2 years and 20% per annum for the next 2 years?

We know the formula for calculating

The compound interest  $C = P1 + \frac{r}{100}n - 1$ where P = amount, r = rate of interest, n = time

Here P = 5000, r1 = 10, r2 = 20

Then  $C = 65001 + \frac{10}{100}2 x 1 + \frac{20}{100}2 - 1= 6500 x \frac{1856}{2500}= \frac{65 x 1856}{25}$

C = Rs. 4826.