Chem/Math Help: Solving Glaucoma Rx

[Zed]

Chem/Math ! Help !

Hi ,

This is a Hw question i have am stuck on i don't know how to solve it ...

A pharmacist is to prepare 16 milliliters of special eye drops for a glaucoma patient. The eye-drop solution must have a 5% active ingredient, but the pharmacist only has 10% solution and 1% solution in stock.


How much of 10% solution should be used to fill the prescription?

How much of 1% solution should be used to fill the prescription?


please help

thx

 

[HallsofIvy]

Let x be the amount of 10% solution, in ml, and let y be the amount of 1% solution, also in ml.

"A pharmacist is to prepare 16 milliliters of special eye drops for a glaucoma patient. "
So x+ y= 16

"The eye-drop solution must have a 5% active ingredient"
In other words, the amount of the active ingredient must be 5% of 16 ml= 0.005*16= 0.08 ml.
The amount of active ingredient in x ml of a 10% solution is 0.1x.
The amount of active ingredient in y ml of a 1% solution is 0.01y

We must have 0.1x+ 0.01y= 0.08.

Solve x+ y= 16 and 0.1x+ 0.01y= 0.08 for x and y.

 

[amcavoy]

Shouldn't that be 0.05*16=0.8?

 

[Zed]

Let x be the amount of 10% solution, in ml, and let y be the amount of 1% solution, also in ml.

"A pharmacist is to prepare 16 milliliters of special eye drops for a glaucoma patient. "
So x+ y= 16

"The eye-drop solution must have a 5% active ingredient"
In other words, the amount of the active ingredient must be 5% of 16 ml= 0.005*16= 0.08 ml.
The amount of active ingredient in x ml of a 10% solution is 0.1x.
The amount of active ingredient in y ml of a 1% solution is 0.01y

We must have 0.1x+ 0.01y= 0.08.

Solve x+ y= 16 and 0.1x+ 0.01y= 0.08 for x and y.

thankx for ur reply ...

after solving it i got 0.8/0.09 but still its giving me answer wrong :S.. i tried solving this way before too still wrong.. although it says to write the answer as an improper fraction. how can i write a decimal as an improper fraction !

thx

Note i did use 5% of 16 as 0.8 so..i don't thinkt hats the problem

 

[Zed]

ok i found x and it turned out to be correct 7.111111111 which is equivelant to 7 and 1/9 as a mixed number...

am found y but its giving me wrong answer.. please tell me if am getting y wrong... i got y to be 8.888888889

 

[HallsofIvy]

Shouldn't that be 0.05*16=0.8?

Hey, arithmetic isn't my strong suit!

(And I couldn't find my calculator.)