Question

A pharmacist is to prepare 15 milliliters of special eye drops for a glaucoma patient. The eye-drop solution must have a 7% active ingredient, but the pharmacist only has 10% solution and 1% solution in stock. How much of each type of solution should be used to fill the prescription?

Answer 1

If there are x mL of 10%, then the rest (15-x) are 1%
Now make sure the amount of active ingredient adds up right:
.10x + .01(15-x) = .07*15
solve for x

Answer 2

1