The Nursing Math Thread

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A member pm'd me the following question highlighted below. We created this thread for you guys to talk about math, solve math problems, and post math websites that you have found helpful.

I was wondering, is there a sticky or a special site that can be coordinated for "math sufferers". Perhaps, beginning calculations or shall i say the basics..simple to complex...step by step on how to calculate. I'm a visual learner, numbers and I don't work well. I am trying, but I've got a block!

Specializes in med/surg, telemetry, IV therapy, mgmt.
Here is another that I am having difficulties since it's sort of "backwards":

1000cc solution of D5NS with 20,000 units of Heparin is infusing at 20ml per hour. The IV set delivers 60 gtts per cc. How many units of Heparin is the pt receiving each hour?

I was figuring that there are 20 units of Heparin per cc (or ml) of D5NS, but how do I figure out the rest? Or do I just multiply the 20 by the gtt, 60, and then divide back with 60 to get the per hour? So, it would be 20 units per hour? Am I doing that correctly?

Thanks.

If you set these up using dimensional analysis (factor label method) as chare did they will be much easier to solve. In doing nursing math like this you are always looking for 3 things:

  • the dose to be given (or ordered)
  • the dose of the medication you have to work with
  • the final amount you will give [usually the answer the question is looking for, but you could be given this figure and asked to solve for one of the other ones above]

Other things that might enter into the problem are:

  • drip factors of IV sets for IV problems
  • conversion factors (when you have to switch from things like liters to milliliters, killograms to pounds or hours to minutes

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Specializes in ICU.

Here's a simple calculation that I'm wondering if it's right. It's basic math.

order: gr i 1/2

available 100 mg tablets

60mg to a gr

1.5 gr is 90mg

give: 9/10 of a tablet? is that right? can you do 9/10 of a tablet?

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Here's a simple calculation that I'm wondering if it's right. It's basic math.

order: gr i 1/2

available 100 mg tablets

60mg to a gr

1.5 gr is 90mg

give: 9/10 of a tablet? is that right? can you do 9/10 of a tablet?

Actually, 1 gr is 60-65mg, so if you do it with 65 you get 97.5mg which you would probably round to 100 since you can't divide a PO med like that.

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Order: Sodium Methicillin 750 mg IM

Label: Sodium Methicillin 1 g dry powder

Reconstitution: add 1.5 mL sterile water for injection to yield 0.5g/mL

How would you guys solve this. Please show me the steps.

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duplicate post removed. :specs:

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order: sodium methicillin 750 mg im

label: sodium methicillin 1 g dry powder

reconstitution: add 1.5 ml sterile water for injection to yield 0.5g/ml

how would you guys solve this. please show me the steps.

it is important to remember when solving these problems that all of your units are expressed the same. this problem can be solved either using dimensional analysis or d/h * q = x formula.

i would suggest that you use dimensional analysis, and show all of your calculations on paper when you first begin working medication math problems. initially, this might take a little longer, however you can easily visualize that you have made all of the necessary conversions. after you become familiar with this method and are comfortable with your abilities you can start using some of the short-cut methods.

to solve this using dimensional analysis:

750 mg * 1 g/1000 mg * 1 ml/0.5 g =
x
(mg and g cross cancel, leaving)

750 * 1/1000 * 1 ml/0.5 =
x

750 * 0.001 * 2 = 1.5 ml

this problem can also be solved using the d/h *q formula: d = desired dose, h = available concentration, and q = volume/quantity in which your available concentration is prepared. again remember, when you are using this formula you need to make your unit conversions as you set up the problem. this method is very similar to the dimensional analysis method, but you are making unit conversions mentally rather than including them in the formula.

to solve this using d/h * q:

750 mg/500 mg * 1 ml =
x
(mg cross cancels)

1.5 * 1 ml = 1.5 ml

i hope this information was helpful. :specs:

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I need to be suscribed to this thread.

me to lol

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wonderful sites! thanks

yes thank you thank you thank you!

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thanks for the sites!!! God bless us!!!

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Another dimensional analysis or factor-label method link. I didn't read through this entire thread to see if it's already been posted. Also has a few practice problems in units conversions, which (glancing at questions in these threads) seem to be what's confusing people the most.

Lesson 2-4 The Factor-Label Method

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http://www.testandcalc.com/quiz/index.asp

This is the one that I used to pass my Dosage and Calculation. We were required to have 100% on the test and I passed it. You should probably also memorize conversions (F to C and lbs to kg especially)

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How Do i solve this problem?

You are to give Aqueous Penicillin 600,000 Units. Available Aqueous Penicillin (powder) 1,000,000 Units per vial. Add 3.6 mL sterile water. Prepared solution will then be 250,000 Units per mL.

What will you give to your client?_____

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