SOLUTION: Brass is made of a mixture of zinc and copper. How many ounces of pure zinc must be mixed with 20 ounces of brass that is 30% zinc and 70% copper to produce brass that is 40% zinc?

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Question 850660: Brass is made of a mixture of zinc and copper. How many ounces of pure zinc must be mixed with 20 ounces of brass that is 30% zinc and 70% copper to produce brass that is 40% zinc?
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Let X be the number of ounces of 100% zinc,
100%2AX%2B30%2A20=40%2A%28X%2B20%29
100X%2B600=40X%2B800
60X=200
X=20%2F6=10%2F3 ounces