Question

Two pipes A and B can fill a tank in 15 hours and 20 hours, respectively, while a third pipe C can empty the full tank in 30 hours. If all the three pipes operate simultaneously, in how much time will the tank, initially empty, be filled?

• A. 12 hours
• B. 15 hours
• C. 18 hours
• D. 13 hours

Answer 1

Answer:

A. 12 hours

pipe A can fill =15 pipe B can fill = 20 pipe C can empty =30 take LCM of these it will be the capacity of tank it is 60 efficiency of A = 60/15=4 efficiency of B = 60/20=3 efficiency of C=60/30=2 (negative) so the all are open then the efficiency = 4+3-2=5 so the time taken for this =60/5=12 hrs