A pharmacist has 600 milliliters of a solution that is 30% active ingredient. How much pure water should she add to the solution to get a solution that is 15% active ingredient?

600 ml of pure water.

Step-by-step explanation:

To determine how much pure water the pharmacist should add to a 600ml solution with 30% active ingredient, so that this solution becomes 15%, the following calculation must be performed:

600 x 0.3 = 180

15 = 180

100 = X

100 x 180/15 = X

18,000 / 15 = X

1,200 = X

1,200 - 600 = 600

Thus, 600 ml of pure water should be added to achieve a 15% solution.