Heparin mL/hr and gtt/min? HELP!

I'm in my first semester of my last year of nursing school and I still struggle with the math. I had to withdraw from classes early last semester so I never got a good handle on figuring out the problems...and there is always the dimensional analysis vs. formula debate ( I typically work with formula...). Can someone explain how to solve this problem and/or recommend a good website?
A newly admitted patient is to recieve 1250 u of heparin per hour continuously. The solution available is 1 L D% 1/4 NS with 50000 u of heparin. Set calibration is 15 gtt/mL. Calculate the hourly flow rate and gtt/min.
(The answer key says 25 mL/hr and 6gtt/min...but im not understanding how they got those answers ) 

Sep 12, '11Well I see how it is 6gtt/min. Use the 25mL/h.
25mL/60 min x 15gtt/mL = 6.25 = round to 6 gtt/min
but I don't see how you can get mL/h... they didn't give you an amount of time.. they just said continuously. But you need the mL/h to get the gtt/min, hopefully someone else can help!Last edit by mgalano on Sep 12, '11 : Reason: spelling 
Sep 12, '11If you have 50,000 units of Heparin in one liter of fluid then you have 50,000 units in 1,000 ml of fluid. Divide 50,000 by 1,000 to get 50. You want to give 1250 units/her of Heparin, and you know that there are 50 units in one ml. Divide 1250 by 50 and you come out with 25 ml/hr to give in order to administer 1,250 units/hour of heparin to the patient. The reason it is in ml/hr is because the heparin has been added to a bag of IV fluid and you already know that you want to give 1,250 units of Heparin an hour. The problem is asking you to figure out how many mls of the IV fluid with Heparin in it you will give per hour in order to give the 1,250 units.
25 ml/hr / 60 minutes x 15 gtt/ml= 6.25. Round that number to 6 gtt/minute. 
Sep 12, '11An excellent site to help you!!!
http://www.dosagehelp.com/
http://www.davesems.com/files/drug_d...lculations.pdf
http://www.simetric.co.uk/si_medical.htmLast edit by Esme12 on Sep 12, '11 
Sep 13, '11My formula is always my desired amount divided by what you have on hand multiplied by the vehicle (ml usually). So you have 1250 units of Heparin ordered and you have 50,000 units of Heparin on hand. So you do 1250/50,000= 0.025 units x 1000ml (I converted the 1 liter to 1000 ml because it's asking you to set the pump in ml/hr) which gives you 25ml/hr. This is what you'd set the pump at. To figure out the drop rate (which would be done if not using a pump and hung by gravity), I use the 'magic number' system as follows:
10gtts tubing=6 (because you want the total drops per minute to equal 60 and 10x6=60)
15gtts tubing=4 (because 15x4=60)
20 gtts tubing=3 (because 20x3=60)
60 gtts tubing=1 (also called mirco drip tubing... because 60x1=60)
So in this instance, you'd take 25 and divide it by the magic number (which in this case, you have a 15 gtts tubing so you'd divide it by 4... 25/4=6.25). You cannot create 0.25 drip so you'd round down to 6 gtts/min.
Does that make sense?