SOLUTION: What rate of interest compounded annually is required to double an investment in 3 years? The rate of interest required is ?% (Round two decimals as needed)

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Question 1087645: What rate of interest compounded annually is required to double an investment in 3 years?
The rate of interest required is ?%
(Round two decimals as needed)

Answer by jorel1380(3719) About Me  (Show Source):
You can put this solution on YOUR website!
Let P be your principal, and r be your annual rate of interest. Then, after 3 years you have:
2P=P(1+r)^3
So:
log 2=log(1+r)^3
log 2=3 log (1+r)
1+r=1.2599210498948731647672106072782
r=26%
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