A sum of ₹ 3000 yields an interest of ₹ 1080 at 12% per annum simple interest in how many years ?

A sum of Rs.1600 gives a simple interest of Rs.252 in 2 years and 3 months. The rate of interest per annum is 

A certain sum of Rs.4200 becomes Rs5523 at 11% p.a simple interest in a certain time. What is the simple interest on the sum of Rs. 4800 at the same rate and in same time period?

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

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?

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?