The interest accrued on a sum of ₹12,000 in two years, when interest is compounded annually, is ₹3,870. What is the rate of interest per annum?

15%

Compound interest = principal × ( 1 + \(\frac{rate}{100 }\) )t  -  Principal

3870 = 12000 × ( 1 + \(\frac{rate}{100 }\) )²  -  12000

15870 = 12000 × ( 1 + \(\frac{rate}{100 }\) )²

\(\frac{15870}{12000 }\) = ( \(\frac{100 + rate}{100 }\) )²

\(\frac{158700}{12 }\)= ( 100 + rate )²

( 100 + rate )² = 13225

100 + rate = 115

Rate = 15%