Calculate compound interest

Question

An investment amount is expected to grow from N$ 13 000 to N$ 18 440.75 in three years when the interest is compounded semi-annually. Calculate the annual interest rate that will give the expected growth.

Answer 1

r is the interest rate that is NOT converted to a decimal...

18.44075 = 13 ( 1+ r/200)^6 <--- divides by 200 because it must be changed to a decimal AND

cut in half due to the semi-annual interested

Solves for r

18.44075/13 = (1 + r/200)^6

200*[root_6(18.44075/13) - 1] = r

8.9341348596864750252626393446027