Question

You need a 20% alcohol solution. On hand, you have a 15 mL of a 5% alcohol mixture. You also have 25% alcohol mixture. How much of the 25% mixture will you need to add to obtain the desired solution?

Answer 1

Let x be the number of mL of 25% alcohol mixture needed.

.05(15) + .25x = .20(15 + x)

.75 + .25x = 3 + .20x

.05x = 2.25

x = 45 mL