What will be the compound interest on 21.000 at 20% per anmm for 1 year compounded half-yearly?

Correct option is D

Given:
Principal (P) = Rs. 21,000, Rate (R) = 20% per annum, Time (T) = 1 year, Compounded half-yearly.

Formula Used:
Compound Interest (CI) = P * (1 + R/(2 * 100))^(2T) - P

Solution:
Rate for 6 months = 20/2 = 10%
​$$Amount = 21,000 * (1 + 10/100)^2\\Amount = 21,000 * (1.1)^2\\$$​​
Amount = 21,000 * 1.21 = Rs. 25,410
CI = Rs. 25,410 - Rs. 21,000 = Rs. 4,410