If A lends ₹6800 to B at 6% per annum simple interest and B lends the same sum to C at 10% per annum simple interest, find the total gain of B in a period of 2 years.

The difference between simple interest and compound interest (compounded half-yearly) on a sum at the rate of 25% per annum for 1 year is ₹ 4,375. What is the principal amount?

A person invested half of his capital at 10% simple interest and the other half at 10% compound interest (compounded annually) for 2 years. If the total interest earned is ₹ 4,100, find his total capital.