Question

Ryan was 8 when his parents invested $4000 in a certificate of deposit that pays 6%. If Ryan leaves the account alone until the investment doubles, how old will he be? (Assume that the interest is not compounded.)

Answer 1

Using the simple interest equation:
\[I=p*i*t\]
With I = total interest gained
p=principal amount
i= interest rate in decimal form
t = time in years

To get a doubled amount the I you want is 4000.
So when you plug in the numbers it equals:
\[4000=4000*.06*t\]

Then you just solve for t. That will give you the number of years to earn the 4000. Just add that to Ryan's age given so 6+t and you get your answer.

Let me know if you need more help.

Answer 2

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