SOLUTION: In my problem a farmer needs 450lbs of chicken feed mixture that is at least 15% protein. The two feeds available are Feed A, which is 18% protein and Feed B, which is 10% protein.

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Question 335595: In my problem a farmer needs 450lbs of chicken feed mixture that is at least 15% protein. The two feeds available are Feed A, which is 18% protein and Feed B, which is 10% protein. Rounded to the nearest pound, how many pounds of each type of feed should he order if he wants 450lbs of a mix that is 15%protein?
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Let A be the amount of feed A, B the amount of feed B.
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Total weight equation
1.A%2BB=450
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Concentration equation
18A%2B10B=15%28450%29
18A%2B10B=6750
2.9A%2B5B=3375
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From eq. 1,
A=450-B
Substitute into eq. 2,
9%28450-B%29%2B5B=3375
4050-9B%2B5B=3375
-4B=-675
B=675%2F4
Then from eq. 1,
A%2BB=450
A%2B675%2F4=1800%2F4
A=1125%2F4
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To the nearest pound,
A=281 lbs
B=169 lbs