Answer:
36 minutes when both pipes are working together
Step-by-step explanation:
capacity of tank = 5400 liters
Pipe A flow per mint. = 5400/90 = 60 liters per mint.
Pipe B flow per mint. = 5400/60 = 90 liters per mint.
Flow of A + B per mint. 60 + 90 = 150 liter per mint.
Therefore, 5400 / 150 = 36 minutes to fill the tank