Simple Interest...

At what rate per cent, a sum of money doubles itself in 15 years?

A sum becomes 28/25 of itself in 5 years, find the rate of interest.

If ₹ 900 amounts to ₹ 1,080 in 4 years at simple interest, what sum will amount to ₹ 1,275 in 5 years at the same rate?

A sum of money doubles itself in 7 years, in how many years it will become four fold ?

A certain sum of money amounted to ₹ 575 at 5% in a time in which ₹ 750 amounted to ₹ 840 at 4%. The rate being the simple interest, what was the sum?

₹ 4,000 is divided into two parts such that if one part be put out at 3% and the other at 5%, the annual interest from both the investments be ₹ 144. Find the first part.

A sum of money amounts to ₹ 767 in 3 years and ₹ 806 in 4 years at the rate of 6%. What is the sum?

In how many years will a sum of money double itself at 12% per annum?

What annual payment will discharge a debt of ₹ 580 due in 5 years, the rate being 8% per annum?

A lent ₹ 600 to B for 2 years and ₹ 150 to C for 4 years and received altogether from both ₹ 90 as simple interest. The rate of interest is: