The interest on a sum of money at 10% p.a. for 2 years with interest being compounded annually is ₹630. Find the simple interest (in ₹) on the same sum at the same rate of interest for 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?