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  1. #1
    Join Date
    Jun 2005
    Location
    Denver, CO
    Posts
    100

    Unanswered: Exponential Decline From Input Box

    I have a large number that a need to make decline exponentially 12 times (12 months) based on a percentage from an input box. I'm rasing the percent decline to the power of .1 ((1-X%)^.1) but this does not seem correct. Any sugestions? Thanks!
    BillS

  2. #2
    Join Date
    Apr 2004
    Location
    Derbyshire, UK
    Posts
    789
    Provided Answers: 1
    Hi

    I think (pehaps) you need somthing like this (for a Decline)

    Number*EXP(-Pct*MonthNumber)

    where

    Number = number to decline (fixed)
    Pct = fixed percentage (as a decimal!)
    MonthNo = 1 to 12


    ??

    MTB

  3. #3
    Join Date
    Jun 2005
    Location
    Denver, CO
    Posts
    100
    I think that's what I want. What would you do if you wanted a 70% decline total in year one?
    BillS

  4. #4
    Join Date
    Apr 2004
    Location
    Derbyshire, UK
    Posts
    789
    Provided Answers: 1
    Hi again

    Still not sure what you are doing, but declining exponetially on a monthly basis by 70% in 12 months (ie to 30% of start value) is given by

    Number*EXP(-Factor*MonthNumber)

    where

    Number = number to decline (fixed)
    Factor = = 0.1
    MonthNo = 1 to 12

    ??

    MTB

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