Posted by Roger on Friday, December 3, 2010 at 10:48am.
With k compounding a year, the compound interest formula becomes:
FV = PV*Rkn
where
FV=future value
PV=present value
r=annual rate of interest, in fraction.
For example, 0.12 stands for 12%.
k=number of compounding a year, 4 for compounding every three months.
n=number of years
R=compounding rate, = 1+r/k
For example,
at 8% annual interest compounded 4 times a year, $10000 will accumulate to $20000 in n years.
20000=10000*(1+0.08/4)4n
divide by 10000,
1.024n = 2.0
take log on both sides
4n log(1.02) = log(2.0)
n = (1/4)log(2)/log(1.02)
=8.75 years
Still not sure what the answer is.
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