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Math Help - Help me Fast for a College Class!!!

  1. #1
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    Help me Fast for a College Class!!!

    Question is: How many gallons of a solution of glycerine and water containing 55% glycerine should be added to 15 gallons of a 20% solution to give a 40% solution??
    please answer me!!!
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  2. #2
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    Quote Originally Posted by Brooke
    Question is: How many gallons of a solution of glycerine and water containing 55% glycerine should be added to 15 gallons of a 20% solution to give a 40% solution??
    please answer me!!!
    Begin, to knowing that,
    \mbox{concetration }=\frac{\mbox{volume of substance}}{\mbox{total volume}}

    Solution 1 has 55% of x gallons is glycerine which is .55x gallons.
    Solution 2 has 20% of 15 gallons is glycerine which is .2\cdot 15=3 gallons.
    Thus when you combine them,
    you have .55x+3 is amount of glycerine.
    and, in total you have,
    x+15
    And you want 40% thus,
    \frac{.55x+3}{x+15}=.4
    Thus,
    .55x+3=.4(x+15)
    Thus,
    .55x+3=.4x+6
    Thus,
    .15x=3
    Thus,
    x=20\mbox{ gallons}
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