SOLUTION: A doctor prescribes an ointment that is 2% hydrocortisone. A pharmacist has 1% and 5% concentrations in stock. How much of each should the pharmacist use to make a 1-ounce tube?

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Question 259556: A doctor prescribes an ointment that is 2% hydrocortisone. A pharmacist has 1% and 5% concentrations in stock. How much of each should the pharmacist use to make a 1-ounce tube?
Found 2 solutions by Fombitz, richwmiller:
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Let A be the amount of 1% and B be the amount of 5%.
Volume equation : A%2BB=1
Concentration equation: A%2B5B=2%28A%2BB%29=2
From the first equation,
A=1-B
Substitute in the second equation,
A%2B5B=2
%281-B%29%2B5B=2
4B=1
B=1%2F4
Then
A=1-B
A=1-1%2F4
A=3%2F4
3/4 oz of 1% and 1/4 oz of 2%.

Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
.01x+.05(1-x)=1*.02
.75 at 1%
.25 at 5%