A sum of money becomes Rs. 2,645 in 2 years at a rate of 15% per annum compounded annually. What will be the simple interest on the same principal amount at 10% per annum in 3 years?

A sum becomes 25 times of itself when invested for 48 years at r% simple interest per annum. Find the compound interest earned if Rs. 51,200 is invested at r% per annum when interest is compounded half-yearly, for 1.5 years.

Simple interest on a certain sum at 4% per annum for 2 years is ₹80. What is the compound interest on the same sum for the same period at the same rate?