Rule of 72 Approximately what interest rate is needed to double an investment over four years?
A)4 percent
B)18 percent
C)25 percent
D)100 percent

Question

Quizplus · Accepted Answer

The rule of 72 states that if you divide 72 by the annual interest rate, you get the number of years it takes for an investment to double. Thus, for an investment to double in 4 years, the interest rate needs to be roughly 18 percent (72/4=18). So, the best choice is B.

Rule of 72 Approximately What Interest Rate Is Needed to Double