How many liters of water do you need to add to 20 liters of a 75% acid solution to get a 9% solution?

To solve problems, first we find the total volume of acid in 20 liters of solution.

We get:

20 * 0.75 = 15 liters of acid.

Find the volume of pure water in the initial solution.

20 – 15 = 5 liters of water.

Since we are adding pure water, we will make the proportion in which 15 liters of acid corresponds to 9%, just as the new volume of solution x refers to 100%.

We get:

x / 100% = 15/9%.

15 * 100 = 9 * x.

1500 = 9 * x.

x = 166 2/3 liters.

We find the amount of water.

166 2/3 – 5 = 161 2/3 liters.

Answer:

You need to add 161 2/3 liters of water.