Question

Two pipes A and B can seperately fill a cistern in 60 min. and 75 min. respectively. There is a third pipe in the bottom of cistern to empty it. If all the three pipes are simultaneously opened, then the cistern is full in 50 min. In how much time third pipe alone can empty the cistern.

• A. 110 min
• B. 100 min
• C. 120 min
• D. 90 min

Answer 1

Answer:

B. 100 min

1/60 + 1/75 - 1/x =1/50 1/x = 1/60 + 1/75 - 1/50 = (5 + 4 - 6)/300 = 3/300 1/x =3/300 х = 300/3 =100 min