Question

Rachel deposited $6449.82 into a savings account with an interest rate of 6.9% compounded annually. About how long will it take for the account to be worth $8000?

Answer 1

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Answer 2

This is a geometric sequence. The formula for that would be
\[Un = U _{1} \times r ^{n-1} \ge 8000\]
So what you need to do is sub in those values
U1 (initial value) = 6449.82
r (interest) = 1.069
Now just sub in and solve for n.

\[Un = 6449.82 \times 1.069^{n-1} \ge 8000\]
Now simply solve it as an inequality.

I hope it helps...