SOLUTION: soybean meal is 18% protein,cornmeal is 9% protein.How many pounds of each should be mixed together in order to get 360-lb mixture that is 17% protein

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Question 545080: soybean meal is 18% protein,cornmeal is 9% protein.How many pounds of each should be mixed together in order to get 360-lb mixture that is 17% protein
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let a = pounds of soybean meal needed
Let b = pounds of cornmeal needed
given:
(1) +a+%2B+b+=+360+
(2) +%28+.18a+%2B+.09b+%29+%2F+360+=++.17+
--------------------------
(2) +.18a+%2B+.09b+=+.17%2A360+
(2) +.18a+%2B+.09b+=+61.2+
(2) +18a+%2B+9b+=+6120+
---------------------
Multiply both sides of (1) by 9,
and subtract (1) from (2)
(2) +18a+%2B+9b+=+6120+
(1) +-9a+-+9b+=+-3240+
+9a+=+2880+
+a+=+320+
and, since
(1) +a+%2B+b+=+360+
(1) +320+%2B+b+=+360+
(1) +b+=+40+
320 pounds of soybean meal are needed
40 pounds of cornmeal are needed
check answer:
(2) +%28+.18a+%2B+.09b+%29+%2F+360+=++.17+
(2) +%28+.18%2A320+%2B+.09%2A40+%29+%2F+360+=++.17+
(2) ++57.6+%2B+3.6+=+.17%2A360+
(2) +61.2+=+61.2+
OK