Alloy of copper and zinc weighing 85 kg contains 40% copper. How much percent will the alloy contain if 15 kg

Alloy of copper and zinc weighing 85 kg contains 40% copper. How much percent will the alloy contain if 15 kg of copper is added to it?

1) An alloy with 40% copper content weighs 85 kg, we calculate the amount of pure copper in this alloy:

40% = 0.4.

85 * 0.4 = 34 (kg) – pure copper.

2) Add 15 kg of pure copper to the alloy. Let’s find the resulting amount of copper:

34 + 15 = 49 (kg) pure copper.

3) We added 15 kg to an alloy weighing 85 kg, we find the weight of the resulting alloy.

85 + 15 = 100 (kg).

4) 100 kg of the resulting alloy contains 49 kg of pure copper. Let’s find the percentage of copper in this alloy:

49: 100 = 0.49.

0.49 = 49%.

Answer: the resulting alloy contains 49% copper.