SOLUTION: how much of an alloy that is 10% copper should be mixed with 400 ounces of an alloy that is 80% copper in order to get an alloy that is 30% copper

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Question 462759: how much of an alloy that is 10% copper should be mixed with 400 ounces of an alloy that is 80% copper in order to get an alloy that is 30% copper
Answer by jorel1380(3719) About Me  (Show Source):
You can put this solution on YOUR website!
.1r+.8(400)=.3(r+400)
.1r+320=.3r+120
.2r=200
r=200/.2=1000
You need 1000 ozs. of 10% copper for your mix.
1400x.3=420
100+320=420..