The compound interest (compounding annually) on a sum of money for the first year is Rs. 600, and for the second year, it is Rs. 660. Find the rate of interest per annum.

Correct option is D

Given:
Compound Interest (CI) for the first year = Rs. 600
Compound Interest (CI) for the second year = Rs. 660
Rate of Interest = ?
Formula Used:
CI for the second year includes interest on the principal and the interest accrued from the first year:
CI for the second year = CI for the first year × $$(1 + \frac R { 100})$$​​
Solution:
Let the rate of interest be R%:
660 = 600 × $$(1 + \frac R { 100})$$​​
$$\frac {660}{600}$$​ = $$(1 + \frac R { 100})$$​
​$$1.1 = 1 + \frac R { 100}$$​​
R = 0.1 × 100 = 10%