Question 446499
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Hi,
Let x represent how much of an alloy that is 40% copper that is needed:
 .40x + .60*100 = .50(100+x)
     .10*100 = .10x
      .10*100/.10 = x
           100 = x

CHECKING our Answer***
 .40*100 + .60*100 = 40 + 60 = 100 = .50*200