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

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

The simple interest on an amount at the rate of 13.5 p.c.p.a. for 10 years is Rs. 765.45. What is the sum?

The simple interest on a sum of money for 3 years is ₹240 and the compound interest on the same sum, at the same rate  for 2 years is ₹170. The rate of interest is 

The simple interest on a certain sum of the money at 4 % per annum for 4 years is Rs.80 more than the interest on the same sum for 3 years at 5 % per annum. Find the sum.

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

The amount of Rs 400 becomes Rs 480 in 4 years. If the rate of interest is increased by 2 percent, how much will it be?

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