SOLUTION: bronze which costs $9.10/kg is made by combining copper which costs $8.90/kg with tin which costs $9.50/kg. Find the number of kg of copper required to make 16.6 kg of bronze?

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Question 728071: bronze which costs $9.10/kg is made by combining copper which costs $8.90/kg with tin which costs $9.50/kg. Find the number of kg of copper required to make 16.6 kg of bronze?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +a+ = kg of copper needed
Let +b+ = kg of tin needed
(1) +8.9a+%2B+9.5b+=+9.1%2A16.6+
(2) +a+%2B+b+=+16.6+
------------------
(1) +890a+%2B+950b+=+15106+
Multiply both sides of (2) by +890+
and subtract (2) from (1)
(1) +890a+%2B+950b+=+15106+
(2) +-890a+-+890b+=+-14774+
+60b+=+332+
+b+=+5.5333+
and
(2) +a+%2B+b+=+16.6+
(2) +a+%2B+5.5333+=+16.6+
(2) +a+=+11.0667+
11.0667 kg of copper is needed
5.5333 kg of tin is needed
check answer:
(1) +8.9a+%2B+9.5b+=+9.1%2A16.6+
(1) +8.9%2A11.0667+%2B+9.5%2A5.5333+=+151.06+
(1) +98.49363+%2B+52.56635+=+151.06+
(1) +151.05998+=+151.06+
close enough