Help.. Math Question

chuckc, BSN, RN · Nov 30, 2005

You take what you want (40mg) divided by what you have on hand (15 mg) and times that by the vehicle (5 ml). Answer is 13.3 or 13 ml. ????????

cn2007rn · Nov 30, 2005

The formula for that problem would be:

Amount Ordered/On Hand x Quantity = Amount you need to give

40mg/15mg x 5ml = 13.3333ml = 13ml

You need to administer 40mg and you have 15mg/5ml, You know that there is 15ml of the med in 5 ml of solution, so you would administer 13 ml's to give 40 mg's of the med.

Hope that helps! :wink2:

VIRGO NURSE · Nov 30, 2005

hi gang.. thanx for responding so quicking..

I got 12.5 and that didn't sound right... I hate pharm...

Daytonite, BSN, RN · Dec 1, 2005

Try this site for help:http://accd.edu/sac/nursing/math/mathindex2.html

Soleilpie · Dec 1, 2005

I'm not sure if this will help, but I was taught in chemistry that the unit I want to end up with as my answer should ALWAYS be on top. So, you have 15mg of drug per 5 mL of some liquid. Well, I need to set up the problem so that I have 5 mL on top. I also need to get rid of the unit "mg" and can do that by setting up the problem where I can cross that unit out. So, my problem looks like:

5mL x 40 mg = 13.3 mL

15mg

Nurse-o-Matic · Dec 2, 2005

Another way to look at this is to first find out how many mL are in one mg. So 15mg in 5 mL= 3 mg in 1 mL. Since you need to dose 40 mg, divide 40 by 3 and you get 13.3333 mL. Get it?