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Math Help - percents

  1. #1
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    percents

    soy meal is 16% protein ; cornmeal is 8% protein. how many pounds of each should be mixed together to get 320-LB mixture that is 15% protein? any idea on how to solve this i hate percents -_-
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  2. #2
    Senior Member eumyang's Avatar
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    Let x = amount of soy meal to be mixed. 16% of this amount is protein, or 0.16x.
    Let y = amount of corn meal to be mixed. 8% of this amount is protein, or 0.08y.

    The total mixture is 320 lb. The first equation represents the amounts mixed overall:
    x + y = 320

    The total mixture is 15% protein, or 0.15(320) = 48. The second equation represents the amount of protein:
    0.16x + 0.08y = 48

    So here we have a system of equations:
    x + y = 320
    0.16x + 0.08y = 48

    Solve for x and y.

    EDIT: Typos.
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  3. #3
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    lets say i switched the numbers to 12% , 6% , 240 lbs , and 7% , i have an answer of 200 although it doesnt look correct because my y is like 12.. cant be right
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  4. #4
    Senior Member eumyang's Avatar
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    This is the system that I'm getting:
    x + y = 240
    0.12x + 0.06y = 16.8

    If you solve this system you should get x = 40 and y = 200.
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