Bissoy.com
Doctors Medicines MCQs Q&A

Pipes A, B and C are attached to an empty cistern. While the first two can fill the cistern in 4 and 10 hours, respectively, the third can drain the cistern, when filled, in 6 hours. If all the three pipes are opened simultaneously when the cistern is half-full, how many hours will be needed to fill the cistern?

Pipes A, B and C are attached to an empty cistern. While the first two can fill the cistern in 4 and 10 hours, respectively, the third can drain the cistern, when filled, in 6 hours. If all the three pipes are opened simultaneously when the cistern is half-full, how many hours will be needed to fill the cistern? Correct Answer 30/11

A and B can fill the cistern in 4 and 10 hours, while C can drain the cistern, when filled, in 6 hours,

Let the capacity of the cistern be 60 units (LCM of 4, 10 and 6)

⇒ A’s 1 hour work = 15 units

⇒ B’s 1 hour work = 6 units

⇒ C’s 1 hour work = -10 units

⇒ (A + B + C)’s 1 hour work = 11

∴ When all the three pipes are opened simultaneously, then they take 30/11 to fill the cistern half.

Related Questions

Pipes A, B, and C are attached to an empty cistern. While the first two can fill the cistern in 6.6 and 16.5 hours respectively, the third can drain the cistern, when filled, in 9.9 hours. If all the three pipes are opened simultaneously when the cistern is three-fifths full, how many hours will be needed to fill the cistern?
Pipes A, B and C are attached to an empty cistern. While the first two can fill the cistern in 4 and 10 hours, respectively, the third can drain the cistern, when filled, in 6 hours. If all the three pipes are opened simultaneously when the cistern is three-fifth full, how many hours will be needed to fill the cistern?
Pipes A, B, and C are attached to an empty cistern. While the first two can fill the cistern in 4 and 10 hours, respectively, the third can drain the cistern, when filled, in 6 hours. If all the three pipes are opened simultaneously when the cistern is three-fifth full, how many hours will be needed to fill the cistern?
Pipes A, B and C are attached to an empty cistern. While the first two can fill the cistern in 4 and 10 hrs, respectively, the third can drain the cistern, when filled, in 6 hrs. If all the three pipes are opened simultaneously when the cistern is half-full, how many hours will be needed to fill the cistern?
A pipe, working at full speed, can fill an empty cistern in 1 hour. However, during the first hour it worked at one-twelfth of its capacity, during the second hour at one-ninth of its capacity, during the third hour at one-sixth of its usual capacity and during the fifth hour it was only one -third as efficient as it was supposed to be. A second pipe also displayed similar performance, but if it worked at full speed would have filled the empty cistern in 2 hours. Together with a drain pipe that drained water out of the tank at a constant rate, the empty cistern could be filled in 5 hours, all the three pipes working concurrently. How many hours will it take the drain pipe to empty the filled cistern if no other pipe was functioning during the time?
Pipes A, B and C are attached to an empty cistern. The first two can fill the cistern in 7 and 10.5 hours, respectively, whereas the third can drain the cistern, when completely filled, in 6 hours. If all the three pipes are turned on simultaneously when the cistern is half-full, how many hours will be needed to fill the cistern?
A pipe, working at full speed, can fill an empty cistern in 1 hour. However, during the first hour it worked at one-twenty-fourth of its capacity, during the second hour at one-twelfth of its capacity, during the third hour at one-eighth of its usual capacity, during the fourth hours at one-fourth of its usual capacity and during the fifth hour it was only one-half as efficient as it was supposed to be. A second pipe also displayed similar performance, but if it worked at full speed would have filled the empty cistern in 2 hours. Together with a drain pipe that drained water out of the tank a constant rate, the empty cistern could be filled in 5 hours, all the three pipe working concurrently. How many hours will it take the drain pipe to empty the filled cistern if no other pipe was functioning during the time?
Two inlet pipes A and B can fill an empty cistern in 35 hours and 52.5 hours respectively while Pipe C is an outlet pipe that can drain the filled cistern in 17.5 hours. When the cistern is full Pipe C is left open for an hour, then closed and Pipe A is opened for an hour, closed and Pipe B is opened for an hour. The process continues till the cistern is empty. How many hours will it take for the filled cistern to be emptied?
Two inlet pipes A & B can fill an empty cistern in 12 hours & 36 hours respectively while Pipe C is an outlet pipe that can drain the filled cistern in 6 hours. When the cistern is full Pipe C is left open for an hour, then closed & Pipe A is opened for an hour, closed and Pipe B is opened for an hour. The process continues till the cistern is empty. How many hours will it take for the filled cistern to be emptied?
There are 12 pipes connected to a tank. Some of them are fill pipes and other are drain pipes. Each of the fill pipes can fill the tank in 8 hours and each of the drain pipes can drain completely in 6 hours. If all the pipes are kept open, an empty tank get filled in 24 hours. How many of the 12 pipes are filled pipes?