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Math Help - ratio and proportions

  1. #1
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    ratio and proportions

    w/5=7/10 solve for w
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  2. #2
    A riddle wrapped in an enigma
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    Quote Originally Posted by abner80 View Post
    w/5=7/10 solve for w
    In a proportion written: w:5 :: 7:10, the product of the extremes (the 1st and 4th terms) = the product of the means (the 2nd and 3rd terms). Knowing this, then

    \frac{w}{5}=\frac{7}{10}

    10w=35

    w=\frac{35}{10}=\frac{7}{2}
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  3. #3
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    Try to get all variables (letters) on one side, numbers on the other. Your problem is that the answer, w, is divided by 5 on the lhs. You must do the opposite (ie multiply by 5) throughout the expression (do it on both sides) to remove the offending 5 and hence get w = ....

    So

    \frac{w}{5}= \frac{7}{10}

    Multiply both sides by 5

    5\times\frac{w}{5}= 5\times\frac{7}{10}

    Do some cancellation on lhs and tidying up on rhs

    w=\frac{7}{2} = 3.5.

    Hope that helps.
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