SOLUTION: if you know your original investment amount (i.e. $1000) and you know your capital doubles every 6 years, how do you determine your interest rate percentage?

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Question 229682: if you know your original investment amount (i.e. $1000) and you know your capital doubles every 6 years, how do you determine your interest rate percentage?
Answer by Edwin McCravy(6935) About Me  (Show Source):
You can put this solution on YOUR website!
if you know your original investment amount (i.e. $1000) and you know your capital doubles every 6 years, how do you determine your interest rate percentage?

If it's simple interest then

I+=+Prt

Then the interest in 6 years must equal the principle P,
so we substitute t=6 and I=P in the above equation
and get

P+=+Pr%286%29
P+=+6Pr

Divide both sides by 6P

%28P%29%2F%286P%29=%286Pr%29%2F%286P%29

%28cross%28P%29%5E1%29%2F%286cross%28P%29%29=%28cross%286P%29r%29%2F%28cross%286P%29%29

1%2F6=r

.162%2F3=r

16%261%2F3%27%25%27=r

Edwin