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 90kg of a 47% copper alloy

Answer 1

x = amount at 15%

90-x = amount of 55%

0.15x + 0.55(90-x) = 0.47(90)

0.15x +49.5 - 0.55x = 42.3

49.5 - 0.40x = 42.3

-0.40x = -7.2

x = -7.2 / -0.4 = 18 kg of 15% copper

90-18 = 72 kg of 55% copper