Question

An auto mechanic has 600 mL of battery acid solution that is 75% acid. He must add water to this solution to dilute it so that it is only 25% acid. How much water should he add?

Answer 1

We know that the acid solution is 600 mL, 75% acid. We need to get a solution with 25% acid.

Based on the given information, we express the following

$0.75\cdot600+0x=0.25(600+x)$

Where x represents water. Let's solve for x

$\begin{gathered} 450=150+0.25x \\ 450-150=0.25x \\ 0.25x=300 \\ x=\frac{300}{0.25} \\ x=1,200 \end{gathered}$

Hence, he has to add 1,200 mL of water.