Compound Interest - General Questions

Find the amount on Rs. 18,000 for 3 years at 10% per annum compounded annually.

Find the amount on Rs. 5,000 for 3 years at 10% per annum compounded annually.

A sum of money doubles itself at compound interest in 5 years. In how many years will it become eight times?

A sum of money doubles itself at compound interest in 7 years. In how many years will it become four times?

A sum amounts to Rs. 3,400 in 2 years and to Rs. 4,250 in 3 years at compound interest. What is the rate of interest?