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

Initial mass = 25 grams

Step-by-step explanation:

`\left((x)/(x+20)\right)\:=\:\:\left((x)/(x+5)\:-.3\:\right)`

x = 20 (mass of copper)

`(20)/(20+5) = .8 = 80` percent

`\\(20)/(20+15) = .5 = 50` percent