Flow rate (gtt/min)= volume/Time(ml/min) X Drop factor(gtt/ml) 400/T X 10gtt/ml = Flow rate(gtt/min) Flow rate = 400 X 10/ T Flow rate = 4000/T Flow rate has been given in the question as 20gtt/min Therefore: 20 = 4000/T T = 4000/20 (min) T = 200minutes And 200 minutes, when converted to hours = 200/60 Because 60minutes = 1 hour T = 3.33 hours 3hours plus -33hours 0-33 hours = 20mins So, he will need another bag at 12:20pm Answer = 12:20pm