A sum of money at double the rate of simple interest doubles itself in 10 years. In how much time will that amount be triple of itself?

The difference between the compound interest and simple interest of a certain sum of amount is rupees 256.40 for 4 years at 10% rate per annum. Find the sum of money?

If the simple interest on ₹ 1 for 1 month is 1 paisa, then the rate percent per annum will be 

A sum of money was invested at a certain rate of simple interest for 2 years. Had it been invested at 1% higher rate, it would have fetched Rs.192 more interest. The sum of money is-

In what time will the annual simple interest rate at $$ {6{1\over4}{\%}}$$ , 72 rupees becomes 81 rupees?

A sum of money becomes two times of itself in 8 years at simple interest, and it becomes four times of itself in 2 years at compound interest, when interest is compounded annually. Find the ratio of the rate of simple interest to the rate of compound interest offered per year.

Rs. 2,000 is invested at 10% p.a. on simple interest. If that interest is added to the principal after every 20 years, the amount will become Rs. 14,000 after

In what time will the simple interest be $$ {2\over5} $$ of the principal at 8% per annum?