The difference between the compound interest (compounded annually) and the simple interest on a sum of ₹10000 at a certain rate of interest for 2 years is ₹121. The rate of interest per annum is:

15% 21% 12% 11%

11%

Difference b/w CI and SI for 2 years = Principal × R% × R% ⇒ 121 = 10000 × \(\frac{R^2}{10000}\) ⇒ R2 = 121 ⇒ R = 11%