Why are the theoretical density values of brass, bronze, and steel reported as a range of densities? how can you categorize these substances?

Theoretical density values  

Explanation:

All of these substances are alloys (a substance made from melting two or more substances, one of them usually being a metal). Brass is a combination of copper and zinc, bronze is mostly copper, tin and other non-metals as well and steel is majorly made up of iron and copper. These alloys have various uses and varying importance in different kinds of industries.

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