Answer:
16 years
Step-by-step explanation:
The rule of 72 says you can estimate the doubling time in years by dividing 72 by the interest rate in percent.
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For an interest rate of 4.5%, the rule of 72 says the doubling time is ...
72/4.5 = 16 . . . years
It will take about 16 years for the investment to double in value.