Question

An alloy of copper and zinc which contains 5 grams of zinc. If 15 grams of zinc are added to this alloy, a new alloy is obtained in which the copper content has been reduced by 30% from the original. Find the initial mass of the alloy

Answer 1

Answer:

Initial mass = 25 grams

Step-by-step explanation:

$\left(\frac{x}{x+20}\right)\:=\:\:\left(\frac{x}{x+5}\:-.3\:\right)$

x = 20 (mass of copper)

$\frac{20}{20+5} = .8 = 80$ percent

$\\\frac{20}{20+15} = .5 = 50$ percent