A sum is invested at 30% simple interest per annum for 2 years. The amount obtained is then reinvested at 10% compound interest per annum for 2 years. If the compound interest from the second investment is Rs 2016, find the original sum?

Let the original sum be Rs P. ATQ, the sum is invested at 30% simple interest per annum for 2 years. So, the amount obtained after 2 years (A) = P + (P * 30 * 2) / 100 Or, A = P + 0.60P = 1.6P Now, this amount (1.6P) is reinvested at 10% compound interest per annum for 2 years. So, the compound interest (CI) from the second investment = A * [(1 + 10/100)^2 - 1] Or, CI = 1.6P * [(1.1)^2 - 1] Or, CI = 1.6P * [1.21 - 1] Or, CI = 1.6P * 0.21 = 0.336P Given that the compound interest from the second investment is Rs 2016. So, 0.336P = 2016 Or, P = 2016 / 0.336 So, P = 6000 Hence, the correct answer is C.