A and B can fill a cistern in 7.5 minutes and 5 minutes respectively and C can carry off 14litres per minute. If the cistern is already full and all the three pipes are opened, then it is emptied in 1 hour. How many litres can it hold? Pipe A in
20
30
80
40
Explanation:
60 minute can pipe in liquid equal to $\dfrac{60}{7.5}$=8 times the capacity of the cistern.
Pipe B in 60 minute can pipe in liquid equal to $\dfrac{60}{5}$=12 times the capacity of the cistern.
Tank was full when all the three pipes were opened. So, pipe C emptied liquid equal to 8+12+1=21 times the capacity of the cistern in 1 hour.
i.e., 21 times the capacity of the cistern =14×60
Capacity of the tank =$\dfrac{14×60}{21}$=40 litre
60 minute can pipe in liquid equal to $\dfrac{60}{7.5}$=8 times the capacity of the cistern.
Pipe B in 60 minute can pipe in liquid equal to $\dfrac{60}{5}$=12 times the capacity of the cistern.
Tank was full when all the three pipes were opened. So, pipe C emptied liquid equal to 8+12+1=21 times the capacity of the cistern in 1 hour.
i.e., 21 times the capacity of the cistern =14×60
Capacity of the tank =$\dfrac{14×60}{21}$=40 litre