SOLUTION: How much of an alloy that is 20% copper should be mixed with 200 ounces of an alloy that is 50% copper in order to get an alloy that is 30% copper?

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Question 115898:
How much of an alloy that is 20% copper should be mixed with 200 ounces of an alloy that is 50% copper in order to get an alloy that is 30% copper?
Answer by checkley71(8403) About Me  (Show Source):
You can put this solution on YOUR website!
.5*200+.2X=.3(200+X)
100+.2X=60+.3X
.2X-.3X=60-100
-.1X=-40
X=-40/-.1
X=400 OUNCES OF 20% COPPER.
PROOF
.5*200+.2*400=.3(200+400)
100+80=.3*600
100+80=180
180=180