At what rate of compound interest per annum will a sum of Rs 10000 becomes Rs 14641 in 4 years?

Given,

Sum = Rs. 10000

Amount = Rs. 14641

Rate = 20% per annum = 10% per 6 month

Now,

Amount = Principal{1 + (rate/100)}time

⇒ 14641 = 10000{1 + (10/100)}time

⇒ 14641/10000 = (11/10)time

⇒ (11/10)4 = (11/10)time

⇒ time = 4

AS, it was compounded half yearly

∴ Actual time of investment = 4/2 = 2 years