A certain sum amounts to ₹ 8,330 in 212 years and to ₹ 10,166 in 512 years at a certain rate per cent per annum, both at simple interest. What will be the simple interest (in ₹) on the same sum in 4 years at double the initial rate?

A sum becomes 2215 of itself in 6 years at simple interest. Find the rate of interest per annum.

In how many years will a sum of ₹5,500 amount to ₹6,600 at a simple interest rate of 5% per annum?

A sum of money amounts to ₹16000 in 6 years at simple interest of 25 percent per annum. What will be the total interest for 6 years?