An alloy weighing 5 kg consists of tin and lead, with a tin content of 40 percent. How much lead must be added to this alloy

An alloy weighing 5 kg consists of tin and lead, with a tin content of 40 percent. How much lead must be added to this alloy to obtain a tin content of 25 percent?

1) Determine the initial weight of tin in the alloy.

Multiply the weight of the alloy by 0.4, since 40% = 40% / 100% = 0.4.

Will:

5 * 0.4 = 2 kg.

2) We make up the proportion.

Let’s write down the weight of the new alloy as an unknown number x.

This weight will be equal to 100%.

In this case, the weight of tin, namely 2 kg, will be equal to 25%.

We get the ratio:

x / 100% = 2/25%.

25 * x = 200.

x = 200/25 = 8 kg (new weight of the alloy).

Find how many kg of lead you want to add.

8 – 5 = 3 kg.

Answer:

To obtain a 25% concentration of tin, add 3 kg of lead.