Question

A pharmacist has 80 milliliters of a 25% saline solution. Which expression can be used to find the percentage concentration of the final solution if she adds x milliliters of a 10% saline solution?

Answer 1

Amount of salt initially = 0.25·80 = 20.
Amount of salt added = 0.10·x = 0.1x.
Total salt = 20 + 0.1x, total volume = 80 + x.

Percentage concentration = ((20 + 0.1x) / (80 + x)) · 100%.