pure copper was mixed with 12% alloy to produce an alloy that was 20% copper.

Question

how much of the pure copper and how much 12% alloy were used to produce 132 kg of the 20% alloy?

Answer 1

So you use "x" as the amount of 100% alloy you're going to put in, and then "132-x" as the amount of 12% alloy you're going to put in (because total there's 132 g).

Convert the % into decimals... you get:

1x + 0.12(132-x) = 0.2(132). The right side b/c there are 132 g of 0.2% copper & the left side should make 132 g of 0.2% copper, so the equations are equal.

x + 15.84 - 0.12x = 26.4

0.88x + 15.84 = 26.4

0.88x = 10.56

x = 12 g

You would need 12 g of 100% alloy, and 110 g of 12% alloy to make 132 g of 20% alloy.