You invested $4000 in a fund for 2 years and was paid simple interest. The total interest that you received on the investment was $320. As a percentage, what was the annual interest rate of your investment?

Answer 1

I = PRT
320 = 4,000 * I * 2
320 = 8,000 I
320/8,000 = I
? = I

Answer 2

(320/2)/4000 * 100 = ? %

Answer 3

I = P*r*t = 320.
4000 * r * 2 = 320,
r = 320/8000 = 0.04 = 4%.