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Thread: Math help

  1. #1
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    Default Math help

    a. .75(x - .5) - 1.6 < .3

    b. Soybean meal is 14% protein; cornmeal is 7% protein. How many pounds of each should be mixed together in order to get 280 pounds of 8% protein?

    c. Find the solution (ordered pair)
    a. .3x-.2y = 4
    b. .4x + .3y = 73/19

    d. Find the solution (ordered pair)
    a. 7x + 6y = -10
    b. -4x + y = 19

    Please show work so I can actually learn how to do it!

    Thank you!

  2. #2
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    a:
    0.75x -0.4 -16 < 0.3
    0.75x - 2 < 0.3
    x - 2.666... < 0.4

    x-2.666... = 0.4
    x = 3.0666..

    every x under 3.0666...
    x < 3.0666...

    Edit:
    b:
    x = amount of soybean meal
    y = amount of corn meal

    (0.14xr + 0.07yr) / (yr+xr) = 0.08
    0.14xr + 0.07yr = 0.08yr + 0.08xr
    0.01yr = 0.06xr
    yr = 6xr ratio between soybean and corn

    x = 280 / 7 * 1
    x = 40

    y = 280 / 7 * 6
    y = 240

    check:

    x * 0.14 = total amount of protein in soybean meal
    y * 0.07 = total amount of protein in corn meal

    40 * 0.14 = 5.6
    240 * 0.07 = 16.8

    total amount of protein = 22.4
    280 * 0.08 = 22.4
    Last edited by masterBB; 07-10-2011 at 09:46 PM.
    Working on: Tithe Farmer

  3. #3
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    Default

    Quote Originally Posted by masterBB View Post
    a:
    0.75x -0.4 -16 < 0.3
    0.75x - 2 < 0.3
    x - 2.666... < 0.4

    x-2.666... = 0.4
    x = 3.0666..

    every x under 3.0666...
    x < 3.0666...
    Wrong answer. Just plug it back in and you'll see it doesn't work.
    Anyways, the way to do #a and #b is attached. C and D use the same concepts as B so I didn't bother.

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    Thanks I see my problem

    a:
    0.75x -0.375 -1.6 < 0.3
    0.75x - 1.975 < 0.3
    x - 2.6333... < 0.4

    x-2.6333... = 0.4
    x = 3.0333..

    every x under 3.0333...
    x < 3.0333...

    Should use my calculator after 11 in the evening.
    Working on: Tithe Farmer

  5. #5
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    Just system of equations.. u can either substitute one into the other or u can multiply them by eachother so that u get an LCF.. Minus or add them and either the X Or Y's should be 0.. then substitute the value back in and bam.. solved..

    a. 7x + 6y = -10
    b. -4x + y = 19

    x = -4, y = -3

    How? Solve by LCF or substitution.. whatever u choose:
    -28x - 24y = 40
    -28x + 7y = 133

    Add them in this case to make x = 0
    0x - 31y = -93
    y = 3

    Sub the value back into either equation to get x:
    7x + 6(3) = -10
    7x = -10 - 18
    7x = -28
    x = -4
    I am Ggzz..
    Hackintosher

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