If a principal amount is invested at compound interest, and it grows to Rs. 8820 in 2 years and Rs. 9261 in 3 years, what was the original principal?

Explanation

Given the amounts after 2 and 3 years under compound interest, the principal is Rs. 8000. This is found by dividing the amount after 2 years by (1 + rate)^2 or by calculating the rate from the increase between years 2 and 3 and then computing the original sum.