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Math Help - Silly Problem I cant figure out with percentage

  1. #1
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    Silly Problem I cant figure out with percentage

    I have 12.00 item for sale i want to mark up 30% that would be 3.60 + 12.00 = 15.60

    now what calculation do i do to get back to 12.00?

    If i have 15.60 and i know i started at 12 how do i get the 3.60?
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  2. #2
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    Re: Silly Problem I cant figure out with percentage

    Hey bjbauer.

    If you added 30%, your new value is 100% + 30% = 130% of the original.

    So algebraically you have new = old * 130% = old * 1.3.

    So if you have new and what to get old, we re-arrange to get

    new/(1.3) = old and since 1.3 = 13/10, we get

    new/(13/10) = (new*10)/13 = old.
    Thanks from HallsofIvy
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  3. #3
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    Re: Silly Problem I cant figure out with percentage

    Just to add a little bit to what chiro said, since you added 30% to the whole, that is a total of 100%+ 30%= 130% as chiro said. That can be written as \frac{130}{100}= \frac{13}{10}. To go back use the reciprocal, \frac{10}{13}. You can calculate that \frac{10}{13}= 0.769, approximately, which you can write as 76.9%.
    Last edited by HallsofIvy; October 12th 2012 at 06:45 PM.
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