A nurse has two solutions(question is in the details box)

Question

A nurse has two solutions that contain different concentrations of a certain medication. One is 12.5% concentration and the other is 5% concentration. How many millitres of each should she mix to obtain 20 millitres of an 8% concentration.

Answer 1

Let x = the number of milliliters of 12.5% concentration

Let y = the number of milliliters of 5% concentration

x + y = 20         x = 20 - y

.125x + .05y = .08(20)

.125(20 - y) + .05y = 1.6

2.5 - .125y + .05y = 1.6

-.075y = -.9

y = 12 milliliters

 

x = 20 - 12

x = 8 milliters