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Chem/Math Help

  1. Sep 6, 2005 #1

    Zed

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    Chem/Math !! Help !!

    Hi ,

    This is a Hw question i have am stuck on i dont 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?


    plz help

    thx
     
  2. jcsd
  3. Sep 6, 2005 #2

    HallsofIvy

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    Staff Emeritus
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    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.
     
  4. Sep 6, 2005 #3
    Shouldn't that be 0.05*16=0.8?
     
  5. Sep 6, 2005 #4

    Zed

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    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 dont thinkt hats the problem
     
  6. Sep 6, 2005 #5

    Zed

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    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.. plz tell me if am getting y wrong... i got y to be 8.888888889
     
  7. Sep 7, 2005 #6

    HallsofIvy

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    Hey, arithmetic isn't my strong suit!

    (And I couldn't find my calculator.)
     
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