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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 -

    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.

  • math -

    i didn't get the right answer :[

    the answer must be 139 months

  • math -

    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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