By volume, one alloy is 60% copper, 30% zinc and 10% nickel. A second alloy is 50% copper, 30% zinc and 20% nickel. The third alloy is 30% copper and 70% nickel. How much of each alloy is needed to make 100 cm^3 of a new alloy that is 40% copper, 15% zinc and 45% nickel?

Answer:

For the first alloy, you need 40 cm^3.
For the second alloy, you need 25 cm^3.
For the third alloy, you need 35 cm^3.