A piece of copper and zinc alloy weighing 48 kg contains 55% copper. How much copper needs

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 the mass of zinc. In the alloy, its content is 100% – 55% = 45%.
Zinc mass: 48kg * 45% / 100% = 21.6kg.
The mass of copper in the alloy was 48kg – 21.6kg = 26.4kg.
After the addition of copper, the zinc content became 100% – 60% = 40%.
This means that the mass of the alloy has become 21.6kg * 100% / 40% = 54kg.
And the mass of copper became 54kg – 21.6kg = 32.4kg.
Added 32.4kg – 26.4kg = 8kg copper.