SOLUTION: An alloy of copper and tin is 20 percent copper. How many pounds of copper must be added to 20 pounds of the alloy in order for the resulting alloy to be 50 percent copper? A)6 B

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Question 614094: An alloy of copper and tin is 20 percent copper. How many pounds of copper must be added to 20 pounds of the alloy in order for the resulting alloy to be 50 percent copper?
A)6
B)12
C)12.5
D)13
E)14
Answer by solver91311(24713) About Me  (Show Source):
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In 20 lbs of 20% copper alloy there are 0.2 * 20 = 4 lbs of pure copper. If you add lbs of pure copper, you will have pounds of 50% alloy, of which is pure copper. Since you started with 4 lbs of pure copper, when you are done you will have lbs of pure copper, so:



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