Ok I haven't had to do drug math in about 10 yrs, I took a test the other noc there were 53 questions 10 math question my score was 43, I did not get one math question right. HELP I can remember 2 question demerol 75mg/2ml dr has ordered 25 mg ___ml to give? heprin 100,000u in 500ml of fl to give 100units qhr and tubing gtt factor is 10? can anyone tell me the formula to use for these? I have the formula some where but I've put it up so good I can't find You all ahve been very helpful in the past and so I thank you for your help now.