Question 957755
First pipe: 1 tank/66min=1/66 tank/min*5/5=5/330 tank/min
Second pipe: 1 tank/55min=1/55 tank/min*6/6=6/330 tank/min
Together: 5/330 tank/min+6/330 tank/min=11/330 tank/min
To fill 1 tank: 1 tank/(11/330 tank/min)=330/11 min=33 minutes.
ANSWER: Using both pipes it takes 33 minutes to fill the tank.