# A piece of copper and zinc alloy weighing 48 kg contains 55% copper.

A piece of copper and zinc alloy weighing 48 kg contains 55% copper. How much copper needs to be added to this piece so that the resulting alloy contains 60% copper?

Let’s find how much copper is contained in the original alloy:

48 * 0.55 = 26.4 (kg) – copper.

Let’s take the amount of copper to be added as x. Then the mass of the new alloy is (48 + x), and the mass of copper in the new alloy is (26.4 + x). Let’s make the proportion:

(48 + x) kg – 100%;

(26.4 + x) kg – 60%.

100 * (26.4 + x) = 60 * (48 + x);

132 + 5 * x = 144 + 3 * x;

2 * x = 12;

x = 6 (kg) – you need to add copper.

Answer: 6 kg of copper must be added to the original piece.

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