SOLUTION: How long will it take for $7 000 to double if it is invested at 6.0% annual interest compounded 9 times a year?

Question 190666: How long will it take for $7 000 to double if it is invested at 6.0% annual interest compounded 9 times a year?
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
Start with the compounding interest formula

Plug in (this is double of 7000), , and

Divide both sides by 7000.

Divide

Combine like terms.

Take the log of both sides

Rewrite the right side using the identity

Divide both sides by .

Approximate the left side

Divide both sides by 9.

Divide

So the answer is approximately which means that it takes about 11.585 years for $7,000 to double
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