Question

how much copper and how much iron should be added to 100% pounds of an alloy containing 25% copper and 40% iron in order to obtain an alloy containing 30% copper and 50% iron?

Answer 1

If x lbs of copper and y lbs or iron are added, then we need

25 + x = .30(100+x+y)
40 + y = .50(100+x+y)

Now just solve for x and y. Be sure to check your answers.

Answer 2

x) 27.5
y)47.5