Damini purchased an item costing ₹7,500 and paid ₹3,500 as a down payment. If simple interest is charged on the remaining amount at 9% per annum, how much interest did Damini pay when clearing all dues after 4 months?

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?