Question

A chemist mixed some 15% saline solution with some 20% saline solution to obtain 200 mL of an 18% saline solution. How many milliliters of the 15% saline solution did the chemist use in the mixture?

Answer 1

Use variables x and y.

.15x + .2y = 200(.18)

Answer 2

x + y = 200
.15x + .2y = .18(200) = .36
.15x - .15y =.15(200) = .-30
.05y = 6

Answer 3

Ohhhhhhhhhh....Thanks!

Answer 4

.05y = 6
y = 120
x = 200 - y = 200 - 120
x = 80 ml