A sum of money doubles itself at compound interest in 15 years. In how many years it  will become eight times?

A man invested a certain sum in scheme A at 15% p.a. for 2 years and earned Rs 1950 as simple interest. He increased his sum by Rs. ‘x’ and invested in another scheme B at 10% p.a. C.I. for 2 years and received Rs. 1680 as compound interest. Find the value of ‘x’. 

A sum of Rs. 8000 will amount to Rs. 8820 in 2 years if the interest is calculated every year. The rate of compound interest is 

The compound interest on Rs. 8,000 at 15% per annum for 2 years 4 months, compounded annually is:

Rachit invests ₹12,000 for a 2-year period at a certain rate of simple interest per annum. Prasad invests ₹12,000 for a 2- year period at the same rate of interest per annum as Rachit, but in Prasad's case the interest is compounded annually. Find the rate of interest per annum if Prasad receives ₹172.80 more as interest than Rachit at the end of the 2-year period. 

If the difference between the compound and simple interest on a certain sum of money for 3 years at 5 % per annum is Rs. 15.25, then the sum is 

A sum of money at compound interest doubles itself in 15 years. It will become eight times of itself in

A sum of ₹4000 is lent out in two parts, one at 8% simple interest and the other at 10% simple interest. If the annual interest is ₹352. The sum lent at 8% is