Question : Two pipes can fill a tank in 15 hours and 4 hours, respectively, while a third pipe can empty it in 12 hours. How long (in hours) will it take to fill the empty tank if all three pipes are opened simultaneously?
Option 1:
Option 2:
Option 3:
Option 4:
Correct Answer:
Solution :
Time to fill the tank by two pipes = 15 hours and 4 hours
Time to empty the tank by third pipe = 12 hours
Efficiency =
Let the total capacity of the tank be LCM of 15, 4, and 12 i.e. 60 units.
The efficiency of the first pipe =
The efficiency of the second pipe =
The efficiency of the third pipe =
Combined efficiency of three pipes = 4 + 15 – 5 = 14
Time to empty the tank by all the pipes together =
Hence, the correct answer is
