Compound Interest - General Questions

The difference between compound interest and simple interest on a certain sum at 12% per annum for 2 years is Rs. 141.12. What is the sum?

What is the compound interest on Rs. 8,400 at 4% per annum for 2 years, compounded annually?

A sum of money doubles itself at compound interest in 6 years. In how many years will it become eight times?

The difference between compound interest and simple interest on a certain sum at 8% per annum for 2 years is Rs. 30.08. What is the sum?

Find the compound interest on Rs. 1,600 at 20% per annum for 1 year, compounded half-yearly.