I am confused and need some help with this math question.

  1. The client with lung cancer is 1 day post-op lobectomy and demonstrates symptoms of infection. The health care provider orders 900 mg of Nafcillin. There is powder in a vial labeled "Nafcillin 1 gram" with instructions "to dilute with 3.4 mL of sterile water to produce 1 gram in 4 mL.".

    How many milliliters does the nurse administer? (Round to the nearest tenth and write only the number.)

    **please let me know some simple steps on how you got the answer. Maybe i am studying too much and my brain is burning out
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  3. by   SaoirseRN
    A simple ratio calculation would work here

    1000mg/4ml = 900mg/x
  4. by   NursingBro
    this is what it says :
    (4 mL/1 gram) X (1 gram/1000 mg) X (900 mg/1) = 3600/1000 = 3.6 mL

  5. by   SaoirseRN
    Yes, that's the answer I got.

    To make this really simple, you need to find out how many mg/ml the solution is.

    1000mg/4ml equals 250mg/ml

    You need 900mg. How many times does 250 go into 900?

    900/250= 3.6
  6. by   NursingBro
    I dont know what is wrong with me sometimes I just cant see it.

    one way i was doing it is 900 / 1000 = 0.9 0.9 x 4 = 3.6

    another weird way is 900 x 4 = 3600 3600/1000 = 3.6

    do you know a website that can help me out with the math? It is tough for me to see it in my mind.
  7. by   PalmHarborMom
    I am in nursing school at the University of South Florida. We use the book Calculating with Confidence 5th Edition by Gray Morris. The book has a website There is some great info on doing calculations and practice problems. You do need to register.
    Last edit by Esme12 on Nov 27, '12 : Reason: TOS/link removed
  8. by   loriangel14
    I use Doc (what the doctor ordered) over stock ( what you have on hand) 900/1000 = 0.9.Multiplied by the volume(4) = 3.6
  9. by   NursingBro
    thanks i will check it out
  10. by   Esme12
  11. by   NursingBro
    Quote from Esme12
    Great website! thanks!
  12. by   Esme12
    You're welcome!
  13. by   mariebailey
    Some simple steps:
    1. Don't forget to convert your g to mg.
    2. Remember the Mass/Liquid for Liquid Formula (found on site previously posted)
    Ordered X Volume have = Liquid Required
  14. by   BloomNurseRN
    I use a similar method to Loriangel14.

    Desired dose/Have * Quantity = X (D/H * Q = X)

    Desired (900 mL)/Have (1000 mL) * 4 mL = 3.6 mL

    Good luck!