Question

A metalworker has a metal alloy that is 15​% copper and another alloy that is 55​% copper. how many kilograms of each alloy should the metalworker combine to create 120 kg of a 39​% copper​ alloy?

Answer 1

Qty · % = Total
Alloy 1: x · 15% = .15x
Alloy 2: 120-x · 55% = .55(120 - x) → 66 - .55x
Mixture: 120 · 39% = .15x + 66 - .55x

120 · .39 = 66 - .40x
46.8 = 66 - .40x
-19.2 = - .40x
48 = x
Alloy 1:x = 48
Alloy 2: 120 - x = 120 - 48 = 72

Answer: The metalworker should use 48 kg of the 15% copper and 72 kg of the 55% copper.