9514 1404 393
Answer:
1200 ounces
Explanation:
Let x represent the weight of 30% copper that needs to be added to the mix. Then the total weight will be (600+x) ounces, and the amount of copper in the mix is ...
0.30x +0.60(600) = 0.40(600 +x)
0.3x +360 = 240 +0.4x . . . . . simplify
120 = 0.1x . . . . . . . . . . . . . subtract 0.3x+240
1200 = x . . . . . . . . . . multiply by 10
1200 ounces of 30% copper should be added to the mix.