SOLUTION: I am not sure how to set this word problem up in order to solve. Tim and Judy mix two kinds of feed for pedigreed dogs. They wish to make 27 pounds of feed worth $0.46 per pound

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Question 776068: I am not sure how to set this word problem up in order to solve.
Tim and Judy mix two kinds of feed for pedigreed dogs. They wish to make 27 pounds of feed worth $0.46 per pound by mixing one kind worth $0.31 per pound with another worth $.077 per pound. How many pounds of the cheaper kind should they use in the mix?

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +a+ = pounds of 31 cents/pound feed needed
Let +b+ = pounds of 77 cents/pound feed needed
---------------
(1) +a+%2B+b+=+27+
(2) +%28+31a+%2B+77b+%29+%2F+27+=+46+ ( in terms of cents )
----------------------------
(2) +31a+%2B+77b+=+1242+
Multiply both sides of (1) by +31+
and subtract (1) from (2)
(2) +31a+%2B+77b+=+1242+
(1) +-31a+-+31b+=+-837+
+46b+=+405+
+b+=+8.804+
and
(1) +a+%2B+b+=+27+
(1) +a+=+18.196+
18.196 pounds of cheaper seed are needed
check:
(2) +%28+31a+%2B+77b+%29+%2F+27+=+46+
(2) +%28+31%2A18.196+%2B+77%2A8.804+%29+%2F+27+=+46+
(2) +%28+564.076+%2B+677.908+%29+%2F+27+=+46+
(2) +1241.984+=+27%2A46+
(2) +1241.984+=+1242+
close enough