If you invest at a rate of return r, divide 72 by r to get the number of years it takes to double your money.

Example 1: r = 10; n = number of years

n = 72 divided r

n = 72 / r

n = 72 / 10

n = 7.2

Example 2: r = 4; n = number of years

n = 72 divided r

n = 72 / r

n = 72 / 4

n = 18

Problem:

1. If you invest at a rate of return 5, how many years will it take to double your money?

2. If you invest at a rate of return 9, how many years will it take to double your money?

3. If you invest at a rate of return 3, how many years will it take to double your money?

4. If you invest at a rate of return 20, how many years will it take to double your money?

5. If you invest at a rate of return 15, how many years will it take to double your money?