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

If the difference between CI and SI for 3 years at the rate of 10% is Rs 31. Find the principle.

If the difference of interest of two banks of Rs 500 is Rs 2.50, find the difference between their rates.

At what annual percentage rate, 10 years of simple interest on an amount will be $$ {2\over 5}$$ of the addition?

A principal increase by 50 percent in five years at the rate of simple interest. What will be the compound interest for 3 years at Rs 20,000 with the same interest rate?

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

At what simple rate of interest a sum is double in 8 years?

A person invests money in three different schemes for 6 years, 10 years and 12 years at 10%, 12% and 15% simple interest respectively. At the completion of each scheme, he gets the same interest. The ratio of his investments is-