SOLUTION: British sterling silver is a copper-silver alloy that is 7.5% copper by weight. How many grams of pure copper and how many grams of British sterling silver should be used to prepa

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Question 642363: British sterling silver is a copper-silver alloy that is 7.5% copper by weight. How many grams of pure copper and how many grams of British sterling silver should be used to prepare 240 grams of a copper-silver alloy that is 16% copper by weight?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let grams of pure copper needed = +c+
Let grams of British sterling silver needed = +s+
+.075s+ = grams of copper in British sterling silver needed
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(1) +c+%2B+.075s+=+.16%2A240+
(2) +.925s+=+.84%2A240+
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(2) +.925s+=+201.6+
(2) +s+=+201.6+%2F+.925+
(2) +s+=+217.95+
Substitute this into (1)
(1) +c+%2B+.075%2A217.95+=+.16%2A240+
(1) +c+%2B+16.35+=+38.4+
(1) +c+=+22.05+
22.05 grams of pure copper are needed
217.95 grams of British sterling silver are needed
check:
(1) +c+%2B+.075s+=+.16%2A240+
(1) +22.05+%2B+.075%2A217.95+=+.16%2A240+
(1) +22.05+%2B+16.35+=+38.4+
(1) +38.4+=+38.4+
OK