Posted by **anonymous** on Wednesday, July 21, 2010 at 9:46pm.

marcia has $220,000 saved for her retirement. How long will it take for the investment to double in value if it earns 6% interest compounded continuously?

- math -
**drwls**, Wednesday, July 21, 2010 at 10:14pm
See http://www.moneychimp.com/articles/finworks/continuous_compounding.htm

for the exact answer (11.56 yrs), or use the "rule of 72*" and get about 12 years.

*The product of the annual interest rate and the number of years must be 72 to double your money.

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**anonymous**, Wednesday, July 21, 2010 at 11:04pm
i didn't get the right answer :[

the answer must be 139 months

- math -
**Anonymous**, Friday, April 27, 2012 at 3:05am
In your case,

440000=220000*e^0.06t

2=e^0.06t

ln2 = 0.06t

t= ln2/0.06

= 11.5524 years x 12 months

=139 months

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