Answer:
The answer is 48 years.
Step-by-step explanation:
The Rule of 72 is used by investors to get a rough estimate of how long an investment will take to double itself with a fixed annual rate of interest. Hence, we divide the given rate of interest by 72 to get a rough estimate.
Here the given information is : Ben put $75 into a CD that pays 1.5% interest compounded monthly
So, time needed to double the CD is \(\frac{72}{1.5}= 48\) years.
