Simple and compound interest

The difference between the simple and the compound interest (compounded annually) on Rs. 1250 for 2 yr at 8% per annum will be

The difference between the simple and the compound interest on a certain sum of money at 4% per annum in 2 years isRs 10. What is the sum?

When the interest is calculated annually, simple interest and compound interest are equal for the first year.