SOLUTION: Hi! I have a problem that has stumped me. Here it is: A nurse has 2 solutions that contain different concentrations of a certain medication. One is a 12% concentration, and t

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Question 414970: Hi! I have a problem that has stumped me. Here it is:
A nurse has 2 solutions that contain different concentrations of a certain medication. One is a 12% concentration, and the other is an 8% concentration. How many cubic centimeters (cc) of each should she mix together to obtain 20 cc of a 9% solution.
So far, I started something like this: .12x + .08x = 20(.09), but not sure that is right and don't know how to plug back into problem to get the concentrations.
THANK YOU SO MUCH!!
Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website!
A nurse has 2 solutions that contain different concentrations of a certain medication.
One is a 12% concentration, and the other is an 8% concentration.
How many cubic centimeters (cc) of each should she mix together to obtain 20 cc of a 9% solution.
:
Let's do it this way
:
Let x = amt of 12% concentration
It say's the result is to be 20 cc, therefore
(20-x) = amt of 8% concentration
:
A typical mixture equation:
.12x + .08(20-x) = .09(20)
.12x + 1.6 - .08x = 1.8
.12x - .08x = 1.8 - 1.6
.04x = .2
x =
x = 5 cc of 12% concentration
then
20 - 5 = 15 cc of 8%
;
:
Check this
.12(5) + .08(15) = .09(20)
.6 + 1.2 = 1.8; confirms our solution