# Thread: Interest problem

1. ## Interest problem

In its first 10 years a mutual fund produced an average annual return of 21.55%. Assume that money invested in this fundcontinues to earn 21.55% compounded annually. How long will it take money invested in this fund to double?

2. ## Re: Interest problem

Compound interest formula:
$A=P(1+i)^n$
P is the principal (initial amount invested)
A is the final amount ...... here A=2*P....(the money invested in this fund doubles)
i = 0.2155
You need to find n.
Hint: It will involve logarithms.
See how you go!

3. ## Re: Interest problem

Geesh...another problem made up by a long-winded teacher; this is plenty:
how long does it take \$1 to double at 21.55% compounded annually?

1.2155^n = 2
solve for n

Thank you!!