IBPS RRB Officer Scale 1 Exam 12 Sep 2020 Prelims Shift 2 Paper

To fill the tank Pipe A and Pipe B takes 12hours. Pipe B and Pipe C takes 9 hours to fill the tank and Pipe C and Pipe A together take 15 hours to fill the tank. Find the time taken to fill the tank when Pipe A, Pipe B and Pipe C opened together(approximately).