SOLUTION: I am trying to find the interest rate "r" in this problem: "At a certain constant APR over the life of the investment, Mara�s $2,000 investment grew to $3,000 in eight years. De

Question 417867: I am trying to find the interest rate "r" in this problem:
"At a certain constant APR over the life of the investment, Mara�s $2,000 investment grew to
$3,000 in eight years. Determine that nominal annual rate of interest (APR), knowing that the
interest rate was constant for those eight years and that interest was compounded annually."
I am using the equation:
A=P(1+r)^t
A being the final investment value, P being the initial investment value, r being the interest rate, and t being the amount of time.
I have gotten as far as this:
0.5 = r^8
I understand that to solve this, I need to use a logarithm, and so I translated it into:
8=log(r) 0.5
but I can't figure out how to solve for "r" after that.
Thank you!

Answer by scott8148(6628) (Show Source): You can put this solution on YOUR website!
3000 = 2000 (1 + r)^8

1.5 = (1 + r)^8

log(1.5) = 8 [log(1 + r)]

[log(1.5)] / 8 = log(1 + r)

1 + r = 10^{[log(1.5)] / 8} ___ this is the inverse of the logarithm operation
RELATED QUESTIONS
Please help with this problem. the interest rate "r" required to increase your... (answered by lwsshak3)

I am having problems with this particular word problem, I know I use the formula : A = P (answered by solver91311)

The formulas we have been using assume that the interest rate is constant over the period (answered by math_tutor2020,ikleyn)

How do I find the rate at which a barrel containing 111 gallons will empty at a constant... (answered by ReadingBoosters)

Please help, I am stucked at this question: Find the interest rate needed for an... (answered by Theo,MathTherapy)

Hello, I've been trying to answer the following for a while now and could really use... (answered by Alan3354)

Didn't know exactly where to put this problem. It's a worksheet and in the text book for... (answered by tutorcecilia)

Can someone please shoe me how to do this word problem with the steps?! I am stuck!... (answered by nyc_function)

Question : A twin-engine plane can fly 800 mi in the same time that it takes a... (answered by ankor@dixie-net.com)