Posted by Sarah on Sunday, November 21, 2010 at 8:09pm.
For r=0.095, with normal compound interest, compounded yearly, the number of years to double at a rate of r% is ln(2)/ln(1+r)=ln(2)/ln(1.095)=7.638 years.
from A=P(1+r)^n
take ln both sides,
ln(A/P)=n ln(1+r)
n=ln(2)/ln(1+r)
With continuous compounding,
A=Pern
Take logs
ln(A/P)=ern
ln(2)=rn
n=ln(2)/r
=ln(2)/0.095
=7.296 years
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