The mass of the alloy of copper and silver is 7.2 kg. The mass of silver is 80% of the mass of copper.

The mass of the alloy of copper and silver is 7.2 kg. The mass of silver is 80% of the mass of copper. How many kilograms of copper is in the alloy?

Let the mass of copper contained in the indicated alloy be equal to the variable a.

Then, in accordance with the conditions of our problem, the mass of silver that is contained in the indicated alloy can be represented as a * 80: 100 = 0.8a.

Since from the condition of our assignment we know for sure that the mass of the specified alloy is 7.2 kilograms, we are able to write down the equation and determine the mass of copper:

a + 0.8a = 7.2;

1.8a = 7.2;

a = 4.

Answer: Under these conditions, the mass of copper is 4 kg.