A Learning Portal from Recruitment India

Home » Aptitude » Pipes & Cisterns » Page 3

To fill a cistern, pipes A, B and C take 20 minutes, 15 minute and 12 minutes respectively. The time in minutes that the three pipes together will take to fill the cistern is:

A.

5 min

B.

7 min

C.

4 min

D.

6 min

Answer with explanation

Answer: Option AExplanation

A can do a piece of work in x minutes

B can do a piece of work in y minutes

C can do a piece of work in z minutes

Minute’s work of each of the three is 1/x +1/y + 1/z

1 minutes work of each of the three pipes = 1/20 + 1/15 + 1/12

= 1/5 or = 5 minutes

Workspace

Two pipes A and B are connected to drain out a water tank. A alone can drain out the tank in 20 hours and B can drain 20 liters per hour. Find the capacity of the water tank given that working together, they require 12 hours to completely drain out the tank.

A.

600

B.

400

C.

800

D.

700

Answer with explanation

Answer: Option AExplanation

Let the capacity of the tank be LCM (20, 12) = 60 units

=> Efficiency of A working alone = 60 / 20 = 3 units / hour

=> Efficiency of A and B working together = 60 / 12 = 5 units / hour

Therefore, Efficiency of B working alone = Efficiency of A and B working together – Efficiency of A working alone

=> Efficiency of B working alone = 5 – 3 = 2 units / hour

=> Time required by B alone to drain the tank = 60 / 2 = 30 hours

But we are given that B can drain the tank at the rate of 20 liters per hour.

Therefore, capacity of the water tank = 20 x 30 = 600 liters

Workspace

Working alone, two pipes A and B require 9 hours and 6.25 hours more respectively to fill a pool than if they were working together. Find the total time taken to fill the pool if both were working together.

A.

6

B.

6.5

C.

7

D.

7.5

Answer with explanation

Answer: Option DExplanation

Let the time taken if both were working together be ‘n’ hours.

=> Time taken by A = n + 9

=> Time taken by B = n + 6.25

In such kind of problems, we apply the formula :

n^{2} = a x b, where ‘a’ and ‘b’ are the extra time taken if both work individually than if both work together.

Therefore, n^{2} = 9 x 6.25

=> n = 3 x 2.5 = 7.5

Workspace

Two outlet pipes A and B are connected to a full tank. Pipe A alone can empty the tank in 10 minutes and pipe B alone can empty the tank in 30 minutes. If both are opened together, how much time will it take to empty the tank completely?

A.

7 minutes

B.

7 minutes 30 seconds

C.

6 minutes

D.

6 minutes 3 seconds

Answer with explanation

Answer: Option BExplanation

Let the capacity of the tank be LCM(10, 30) = 30 units. => Efficiency of pipe A = 30 / 10 = 3 units / minute => Efficiency of pipe A = 30 / 30 = 1 units / minute => Combined efficiency of pipe A and pipe B = 4 units / minute Therefore, time required to empty the tank if both pipes work = 30 / 4 = 7 minutes 30 seconds

Workspace

two pipes A and B can fill a tank in 12 minutes and 15 minutes respectively. If both the taps are opened simultaneously and the tap A is closed after 3 minutes, then how much more time will it take to fill the tank by tap B?

A.

7 min 15 sec

B.

7 min 45 sec

C.

8 min 5 sec

D.

8 min 25 sec

Answer with explanation

Answer: Option DExplanation

Let the total capacity of the tank be 60 units. (a multiple of 12 and 15)

So the efficiency of tap A = 60/12 = 5 units/min

efficiency of tap B = 60/15 = 4 units/min

Initially both taps are opened, so they will fill 5+4= 9 units in 1 min.

In 3 minutes they will fill 27 units.

Remaining tank to be filled is 60-27 = 33 units

Now as per the question only tap B operates which will take 33/4 = 8.25 minutes.

Workspace

A.

30 hours

B.

15 hours

C.

10 hours

D.

6 hours

Answer with explanation

Answer: Option BExplanation

Suppose the first pipe alone can fill the tank in xx hours. Then,

second pipe alone can fill the tank in (x−5)(x−5) hours,

third pipe alone can fill the tank in (x−5)−4=(x−9) hours.

Part filled by first pipe and second pipe together in 1 hr

= Part filled by third pipe in 1 hr

Workspace

Pipe A usually fills a tank in 2 hours. On account of a leak at the bottom of the tank, it takes pipe A 30 more minutes to fill the tank. How long will the leak take to empty a full tank if pipe A is shut?

A.

2 hours 30 minutes

B.

5 hours

C.

4 hours

D.

10 hours

Answer with explanation

Answer: Option DExplanation

Pipe A fills the tank normally in 2 hours.

Therefore, it will fill 1/2 of the tank in an hour.

Let the leak take x hours to empty a full tank when pipe A is shut.

Therefore, the leak will empty 1/x of the tank in an hour.

The net amount of water that gets filled in the tank in an hour when pipe A is open and when there is a leak = (1/2 – 1/x) of the tank. —– (1)

Now, when there is a leak, the problem states that it takes two and a half hours to fill the tank. i.e. 5/2hours.

Therefore, in an hour, 2/5th of the tank gets filled. —– (2)

Equating (1) and (2), we get 1/2 – 1/x = 2/5

=> 1/x = 1/2 – 2/5 = 1/10

=> x = 10 hours.

Workspace

A.

120 liters

B.

240 liters

C.

180 liters

D.

60 liters

Answer with explanation

Answer: Option BExplanation

A fills 4 buckets in 24 minutes. Thus, A fills 1 bucket in 24/4 = 6 minutes

Similarly, B fills 8 buckets in 1 hour. Thus B fills 1 bucket in 60/8 minutes

Similarly, C fills one bucket in 20/2 = 10 minutes

In 2 hours,

Number of buckets filled by A will be = 120/6 = 20 buckets

Number of buckets filled by B will be = 120/ (60/8) = (120 * 8) / 60 = 16 buckets

Number of buckets filled by C will be = 120 / 10 = 12 buckets

Total number of buckets filled = (20 + 16 + 12) = 48 buckets

Total amount of water coming out of the tank = capacity of the tank = 48 * 5 liters = 240 liters

Workspace

** **A tank has a leak which would empty it in 10 hours,a tap is turned on which admits 4 litre a minute into the tank and now it emptied in 12 hours.The capacity of the tank is:

A.

648 litres

B.

1440 litres

C.

1200 litres

D.

1800 litres

Answer with explanation

Answer: Option BExplanation

Let speed of the bike be x km/hr. Let speed of the electric car be y km/hr

∴ 200/x + 600/y = 10 ∴ 300/x + 500/y = 11

Part filled in 1 hour

= (1/10-1/12) = 1/60

Time taken to fill the tank = 60 hours

Water filled in 60 hours =4*60*60=1440 litres

Workspace

Two pipes A and B can fill a tank in 20 and 16 hours respectively. Pipe B alone is kept open for 1/4 of time and both pipes are kept open for remaining time. In how many hours, the tank will be full?

A.

18 1/3 hrs

B.

20 hrs

C.

12 1/4 hrs

D.

10 hrs

Answer with explanation

Answer: Option DExplanation

** **Let the required time be x hours, then

⇒ x/16+3x/80 = 1⇒ x= 11=10 hours.

Workspace

Pipe M and N running together can fill a cistern in 6 minutes. If M takes 5 minutes less than N to fill the cistern, then the time in which N alone can fill the cistern will be

A.

15 min

B.

10 min

C.

30 min

D.

25 min

Answer with explanation

Answer: Option AExplanation

Let pipe M fills the cistern in x minutes.

Therefore, pipe N will fill the cistern in (x+5) minutes.

Now, 1/x + 1/(x+5) = 1/6 → x = 10

Thus, the pipe M can fill in 10 minutes, so N can fill in 10+5 =15 minutes.

Workspace

A tank is filled in 5 hours by three pipes A, B and C. The pipe C is twice as fast as B and B is twice as fast as A. How much time will pipe A alone take to fill the tank

A.

20 hours

B.

25 hours

C.

35 hours

D.

Cannot be determined

Answer with explanation

Answer: Option CExplanation

Suppose pipe A alone takes *x* hours to fill the tank.

Then, pipes B and C will take | x |
and | x |
hours respectively to fill the tank. |

2 | 4 |

1 | + | 2 | + | 4 | = | 1 | |

x |
x |
x |
5 |

7 | = | 1 | |

x |
5 |

*x* = 35 hrs.

Workspace

Two pipes A and B can fill a tank in 15 and 3 minutes respectively. If both the pipes are used together, then how long will it take to fill the tank?

A.

150 sec

B.

15 sec

C.

9 minutes

D.

12 minutes

Answer with explanation

Answer: Option AExplanation

As per given statements,

In 1min, part filled by pipe A = 1/15

In 1min, part filled by pipe B fills = 1/3

Together, in 1min, they fill = (1/15) + (1/3) = 2/5 part

Therefore, together they fill the tank in 5/2min = 150sec

Workspace

One pipe can fill a tank three times as fast as another pipe. If together the two pipes can fill tank in 36 min, then the slower pipe alone will be able to fill the tank in ?

A.

144 min

B.

94 min

C.

187 min

D.

85 min

Answer with explanation

Answer: Option AExplanation

Let the slower pipe alone fill the tank in x min.

Then, faster pipe will fill it in x/3 min.

1/x + 3/x = 1/36

4/x = 1/36 => x = 144 min.

Workspace

Two pipes A and B can fill a tank in 15 minutes and 20 minutes respectively. Both the pipes are opened together but after 4 minutes, pipe A is turned off. What is the total time required to fill the tank?

A.

14 min. 40 sec.

B.

12 min. 30 sec.

C.

11 min. 45 sec.

D.

10 min. 20 sec.

Answer with explanation

Answer: Option AExplanation

Workspace

Correct Answer 👍

Wrong Answer 👎

RecruitmentIndia.in is Blog where we will update the information by exploring various online and offline sources of information. Our aim is to provide the latest Education related news as fast as possible to the students for free of cost.

Exams.Recruitmentindia.in is a Preparation portal where you can prepare all the competitive related questions like Aptitude, Reasoning, English Questions and Current affairs for free of cost

You can Contact us at :