A pharmacist has a 10% alcohol solution and a 25% alcohol solution. How many milliliters of each solution will she need to mix together in order to have 200 mL of a 20% alcohol solution?

1 Answer
Mar 10, 2018

Answer:

10% solution #= 66.67 mL#
25% solution #= 133.33mL#

Explanation:

Let us begin by assigning volume values to each of the solutions.

We will make the #10%# solution #x#
This will make the #25%# solutions #200-x#
The final #20%# solution will be #200ml#

The equation for combining the solutions becomes

#.10(x) + .25(200-x) = .20(200)#

#.1x + 50 -.25x = 40#

#.1x cancel(+ 50) -.25x cancel(- 50) = 40 -50#

#-.15x = -10#

#(cancel(-.15)x)/(cancel(-.15)) = -10/-.15#

# x = 66.67 mL#

#200-x = 133.33mL#