The difference between the simple and compound interest for a certain sum of money of 3 years at 5% per annum is Rs. 61.0. Find the sum

5% interest compounded annually for 3 years multiplies the initial balance by

... 1.05^3 = 1.157625

5% simple interest for 3 years multiplies the initial balance by 1 + 3*0.05 = 1.15.

The difference of these multipliers is

... 1.157625 - 1.15 = 0.007625

If the difference in account balance is Rs 61.00, then the invested principal amount P is

... P*0.007625 = 61.00

, ... P = 61.00/0.007625 = 8000.00

The sum of money is Rs 8000.