# To reduce 16 ounces of a 25% solution of antiseptic to a 10% solution, how much distilled water should a nurse add?

##### 1 Answer

#### Explanation:

Here's a more intuitive approach to use here.

You know that your initial solution has a percent concentration, presumably *volume by volume*, of **any volume** of this solution contains **part** solute and **parts** solvent.

The target solution must have a concentration of **any volume** of this solution will contain **part** of solute and **parts** solvent.

Your starting solution has a volume of **ounces**, or **parts**, each with a volume of **ounces**.

In order to get to a solution that has a total of **parts**, you must add **parts** of solvent to the initial solution. Since we know that

#"1 part " = " 4 ounces"#

it follows that you must add

#6color(red)(cancel(color(black)("parts"))) * "4 ounces"/(1color(red)(cancel(color(black)("part solvent")))) = "24 ounces"#

of distilled water, which is your solvent, to the initial solution.

The target solution will contain **part** solute and **parts** distilled water for a total of **parts** of solution, and hence have a percent concentration of