Model 1 Basic Pipes & Cisterns problems Section-Wise Topic Notes With Detailed Explanation And Example Questions

Question : 1

A cistern is provided with two pipes A and B. A can fill it in 20 minutes and B can empty it in 30 minutes. If A and B be kept open alternately for one minute each, how soon will the cistern be filled ?

a) 120 minutes

b) 121 minutes

c) 110 minutes

d) 115 minutes

Question : 2

A cistern can be filled with water by a pipe in 5 hours and it can be emptied by a second pipe in 4 hours. If both the pipes are opened when the cistern is full, the time in which it will be emptied is :

a) 20$1/2$ hours

b) 9 hours

c) 18 hours

d) 20 hours

Question : 3

Two pipes can fill a tank in 15 hours and 20 hours respectively, while the third can empty it in 30 hours. If all the pipes are opened simultaneously, the empty tank will be filled in

a) 15$1/2$ hours

b) 10 hours

c) 12 hours

d) 15 hours

Question : 4

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

a) 90 minutes

b) 110 minutes

c) 100 minutes

d) 120 minutes

Question : 5

A pipe can fill a tank in x hours and another can empty it in y hours. They can together fill it in (y > x)

a) ${xy}/{x - y}$ hours

b) ${xy}/{y - x}$ hours

c) x - y hours

d) y - x hours