# A chemist has 400 grams of salt solution that is 10% salt. How many grams of 20% salt solution must be added to obtain a 12% solution of salt?

##### 1 Answer

You need to add **100 g** of the 20% salt solution.

#### Explanation:

So, you're dealing with two salt solutions of different percent concentrations by mass.

Start by calculating how much salt you get in the 400-g sample of the 10% solution.

Now, let's say that the mass of the 20% solution needed is equal to **20 g** of salt for every **100 g** of solution, you can say that

The *taol mass of the salt* in the target 12% solution will be

The *total mass of the target solution* will be

This means that you can write

Rearrange and solve this equation for

This means that if you add **100 g** of the 20% solution to **400g** of the 10% solution, you will get **500 g** of a 12% salt solution.