Again a Math question

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Hi

I am sitting here and can not figure out the diffrence?

I am startting my first nursing job in the US and i will have to take a math test for my new employer... I have got some papers to review and learn from them and i can not find out why these are different:

D Desired (Amt ordered)

_ Divided by

OH On Hand ( or Amt of mixture= ml,cc,units, etc)

Example: Dr has ordered Demerol 75mg for your Pat. The Demerol on hand is in a concentration of 50mg/2 ml How many total ml will you give to your Pat?

75 divided by 50mg/2ml = 1.5 ml

Ex: Dr has ordered Demerol 75mg It comes packaged (on hand) Demerol 50mg/ 2ml

Set up 75mg X xml

_ _

50 mg 2ml

cross multiply

75mgX2ml=150mg/ml 50 mgX xml=50mg/xml= 150mg/ml divided by 50mg/mlx= 3ml

How is this to understand?

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Specializes in ob, med surg.

I'm not sure this will help but try this:

How much of the drug is ordered for the patient?

Ordered amount = 75mg

You don't know how many ml you will need so that amount = X ml

How much of this drug do you have on hand?

You have 50mg per 2ml

Set the problem up as a ratio...What do you need compared to what do you have.

YOU 75mg YOU 50mg

NEED Xml HAVE 2ml

Now cross multiply

75mg x 2ml = 150mg/ml

50mg x Xml = 50Xmg/ml

This should be written as

150mg/ml = 50Xmg/ml

Now you need to get that X to stand alone. So you divide both sides of the equation by 50mg

So

150mg/ml = 50Xmg/ml

50mg 50mg

You are left with

3ml = Xml

Get a piece of paper, go slow, and remebmber that it is a ratio.

I hope it helps. I feel your frustration. Takes me a long time to do dosage problems, but I'm never wrong!

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Specializes in ob, med surg.

I just realized the problems don't line up on site exactly as I typed them. Email me if you still are confused.

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Specializes in Med Surg/Tele/ER.
Hi

I am sitting here and can not figure out the diffrence?

I am startting my first nursing job in the US and i will have to take a math test for my new employer... I have got some papers to review and learn from them and i can not find out why these are different:

D Desired (Amt ordered)

_ Divided by

OH On Hand ( or Amt of mixture= ml,cc,units, etc)

Example: Dr has ordered Demerol 75mg for your Pat. The Demerol on hand is in a concentration of 50mg/2 ml How many total ml will you give to your Pat?

75 divided by 50mg/2ml = 1.5 ml

Ex: Dr has ordered Demerol 75mg It comes packaged (on hand) Demerol 50mg/ 2ml

Set up 75mg X xml

_ _

50 mg 2ml

cross multiply

75mgX2ml=150mg/ml 50 mgX xml=50mg/xml= 150mg/ml divided by 50mg/mlx= 3ml

How is this to understand?

I am not sure if this is what you are asking or not but...DO/DA x amount..would be 75mg/50mg x 2ml=3ml..(we say dose ordered/dose available X's amount) (75/50=1.5 X 2=3)

Now for the Dimensional analysis method you start out w/what you want end result to be...ml=2ml/50mgx75mg/1=150/50=3ml

cross out matching amts. here it is mg. then all you are left w/is ml...which is what you want your answer to be. If you are confused here is a good site http://www.dalesplace.net/factor.htm I am usless w/ratio porp. method. Good luck

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