18. Two pipes A and B can separately ill a cistern in 60 minutes and 75 minutes respectively. There is apipe at the bottom of the cistern to empty it. If all the three pipes are simultaneously opened, thenthirdhe cistern is full in 50 minutes. In how much time can the third alone empty the cistern?(a) 110 minutes(b) 100 minutes(c) 120 minutes(d) 90 minutes

18. Two pipes A and B can separately ill a cistern in 60 minutes and 7

1.	18. Two pipes A and B can separately ill a cistern in 60 minutes and 75 minutes respectively. There is apipe at the bottom of the cistern to empty it. If all the three pipes are simultaneously opened, thenthirdhe cistern is full in 50 minutes. In how much time can the third alone empty the cistern?(a) 110 minutes(b) 100 minutes(c) 120 minutes(d) 90 minutes
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