# The alloy includes copper, tin and antimony in a ratio of 3: 11: 6. Find the percentage of copper

**The alloy includes copper, tin and antimony in a ratio of 3: 11: 6. Find the percentage of copper, tin and antimony in this alloy. What is the mass of an alloy if it contains 4 kg more tin than copper?**

Let’s find how many parts the alloy contains:

1) 3 + 11 + 6 = 20 (h.)

The mass of the entire alloy is 100%, we find how many percent are for each part:

2) 100/20 = 5 (%).

Then if copper is 3 parts:

3) 5 * 3 = 15 (%) – the percentage of copper.

If tin is 11 parts:

4) 5 * 11 = 55 (%) – tin.

Antimony 6 parts, which means:

5) 5 * 6 = 30 (%) – antimony.

Let’s find how many parts of tin are more than copper:

6) 11 – 3 = 8 (parts).

Because 4 kg = 4000 g, then 8 parts have a difference of 4000 g and one part:

7) 4000/8 = 500 (g).

Since there are only 20 parts in the alloy, the mass will be equal to:

8) 500 * 20 = 10000 (g)

Or 10,000 g = 10 kg.

Answer: in an alloy of copper 15%, tin 55%, antimony 30%, the mass of the alloy is 10 kg.