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Math Help - trying to work out what probably is a pretty basic formula.

  1. #1
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    trying to work out what probably is a pretty basic formula. (solved)

    i'm trying to work out what steps i need to take to calculate the number that makes the following true...

    (719 + 728 + 692 + 719 + X) / 5 = (719 + 728 + X) / 3



    i know the answer is about 670 but don't know how to work it out.

    can anyone help?
    Last edited by val1; August 15th 2010 at 01:14 AM. Reason: solved
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  2. #2
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    First it would help if you'd learn some LaTeX, so people can actually read what you've posted...

    I assume it's

    \frac{719+728+692+719+x}{5} = \frac{719+728+x}{3}

    \frac{2858+x}{5} = \frac{1447 + x}{3}

    3(2858 + x) = 5(1447 + x)

    8574 + 3x = 7235 + 5x

    1339 = 2x

    x = 669.5.
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  3. #3
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    ok, sorry about that. but that's excellent, i can see what i needed to do. i appreciate that a lot.
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