Question

Use the Rule of 72 to solve. Manny has his money in a savings account earning 4.5% interest. How long it will take his money to double?

Answer 1

If Manny's initial money in the savings account is x, we are to calculate for the period in which Manny's money becomes 2x. The calculations are shown 
                                               2x = x (1.045)^n
Cancelling both x from the equation and the computing for value of n will give us an answer of 15.75 years. 

Answer 2

Answer: 16 years is how long it will take for his money to double.