Math help from the Learning Centre - Centennial College The formula can be arranged to solve for the time and volume. T i m e = V o l u m e F l o w R a t e V o l u m e = F l o w R a t e × T i m e Examples: 1. An order of Lactated Ringer's at 167 mL/h IV for 6 hours. How many millilitres will the patient receive in 6 hours?