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Math Help - Simple Weighted Average

  1. #1
    Senior Member sfspitfire23's Avatar
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    Simple Weighted Average

    Hi guys-

    I am calculating a weighted average like so-

    (10/100) * 5 + (40/100) * 10 + (40/100) * 20 + (10/100) * 0 = 12.5

    Notice the zero at the end of the right side of the equation.

    Now, what if I want the solution of the equation to be 12? Is there a way to mathematically reset the weights so that 12 is the answer? I was thinking that it might be possible to remove the same amount of weight from each number like so-

    ((20-x) / 100) * 5 + ((40-x) / 100) * 10 + ((40-x) / 100) * 20 + (3* x / 100) * 0 = 12.


    I would then solve for x, allocate the unneeded weight to 0, and have 12 be the answer. Is there a better, more rigorous way to re-weight things? Anything involving proportions?

    Thanks
    Last edited by sfspitfire23; June 27th 2013 at 07:25 PM.
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  2. #2
    MHF Contributor
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    Re: Simple Weighted Average

    Hey sfspitfire23.

    In general you need a model for re-weighting all the weights. You have shown one model where you allocate 3x to the final weight and subtract x from the existing weights but this is only one way of re-distributing the weights.

    In short, there is no single answer to your question: it depends on how exactly you want to re-distribute the weights specifically.
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