From 500 kg of ore with 15% copper content, 60 kg of copper were obtained. How much copper was lost?

Let’s find what percentage is 60 kg from 500 kg. Let’s make a proportion, take 500 kg as 100%:

500 kg – 100%;

60 kg – x%.

Find x by multiplying the copper weight by 100% and dividing by the ore weight:

x = 60 * 100: 500 = 12%

Now we can find out how many percent of copper was lost. Subtract 12% from the percentage of copper in the ore:

15 – 12 = 3% was lost.

Answer: 3% was lost.