Simple Interest - General Questions

At 10% per annum simple interest, what principal yields Rs. 2,500 as interest in 5 years?

At 8% per annum simple interest, what principal yields Rs. 480 as interest in 2 years?

At 10% per annum simple interest, what principal yields Rs. 1,800 as interest in 2 years?

What is the simple interest on Rs. 9,500 at 8% per annum for 6 years?

In how many years will a sum of money double itself at 4% per annum simple interest?