The simple interest on a sum of money at 10% per annum for 2 years is ₹ 8,100. Compounded annually, what would be the compound interest (in ₹) on the same sum for the same period at the same rate of interest?

8,505

Simple Interest = Rs 8100

Rate =  10 %

Time = 2 years 

Simple Interest for 2 years = R%+ R%  =  10% +  10%  =  20% 

Compound Interest for 2 years = R%+ R% + \(\frac{R% × R% }{100}\) = 10% + 10% + 1% = 21%

A.T.Q ,

   ⇒ 20% =  Rs 8100

   ⇒ 1%   =  Rs \(\frac{8100}{20}\)   

   ⇒ 21% =  Rs \(\frac{8100}{20}\)  × 21

               = Rs  8505