Question

Double your money—Rule of 72. Approximately how long will it take to double your money if you get an annual return of 3.6%​, 7.1%​, or 9.8% on your​ investment?  

Approximately how long will it take to double your money if you get a 3.6​% annual return on your​ investment?

Answer 1

As per Rule 72, the number of years it takes to double an investment = 72 / rate of return

When annual return is 3.6%.

approximate time period to double = 72 / 3.6=>20 years.

When annual return is 7.1%.

approximate time period to double = 72/9.1 =>7.9 years .

When annual return is 9.8%

approximate time period to double = 72/9.8 =>7.35 years