What is the rate of interest per annum for simple interest at which Rs.880 amounts to Rs.913 in $$1{1\over 2}$$years?

On a sum Rina earn a interest of Rs. 1519 at S.I. in 7 years at 7% p.a. Find the sum.

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

In 5 years, the simple interest on an amount of Rs. X is $$2\over 5$$ of the principal. The rate of interest per annum is:

Manoj deposited ₹ 29400 for 6 years at a simple interest. He got ₹ 4200 as interest after 6 years. The annual rate of interest was-

There is 80% increase in an amount in 8 years at simple interest. What will be the compound interest on Rs. 15,000 after 3 years at the same rate of interest?

In what time will ₹ 72 become ₹ 81 at $$6{1\over4}$$ % per annum simple interest?

What will be the ratio of the interests earned by identical sum of money invested at the same rate of simple interest for 6 years and for 15 years respectively?