SOLUTION: An alloy of tin and copper contains 16% tin. How much tin (to the nearest tenth) must be added to make 820 pounds of alloy that is 18% tin?

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Question 913696: An alloy of tin and copper contains 16% tin. How much tin (to the nearest tenth) must be added to make 820 pounds of alloy that is 18% tin?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
The wording is VERY confusing, and I have done
many, many of this exact type of problem- nuf said
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+820%2A.16+=+131.2+ = pounds of tin in 16% alloy
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Let +x+ = pounds of pure tin to be added
+%28+131.2+%2B+x+%29+%2F+%28+820+%2B+x+%29+=+.18+
+131.2+%2B+x+=+.18%2A%28+820+%2B+x+%29+
+131.2+%2B+x+=+147.6+%2B+.18x+
+.82x+=+147.6+-+131.2+
+.82x+=+16.4+
+x+=+20+
20 pounds of tin must be added to
the 16% alloy
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check:
+%28+131.2+%2B+x+%29+%2F+%28+820+%2B+x+%29+=+.18+
+%28+131.2+%2B+20+%29+%2F+%28+820+%2B+20+%29+=+.18+
+151.2+%2F+840+=+.18+
+151.2+=+151.2+
OK