The alloy includes copper-tin-zinc in a ratio of 12:13:25. What is the percentage of copper?

First, we determine the sum of all parts of the alloy.

To do this, we summarize the values of copper, tin and zinc from the ratio.

We get:

13 + 12 + 25 = 50 equal parts.

We accept the weight of the alloy as 100%.

We find how many percent of the total alloy is 1 part.

To do this, we divide the entire alloy by the number of parts.

100% / 50 = 2%.

We know that the proportion of copper in the alloy is 12.

In this case, in order to find its percentage, we multiply the number of parts by 2%.

Will be:

12 * 2% = 24%.

Answer: The alloy contains 24% copper.