math
posted by sakena on .
Anne and Nancy use a metal alloy that is 23.5% copper to make jewelry. How many ounces of a
21% alloy must be mixed with a 30% alloy to form 108 ounces of the desired alloy?

you want the final 108 oz to be 23.5% copper. That means it contains 25.38 oz of copper
So, if there are x oz of 21% alloy,
.21x + .30(108x) = .235(108)
.21x + 32.4  .30x = 25.38
.09x = 7.02
x = 78
so, she uses 78 oz of 21% and 30 oz of 30%