All questions of Pipes and Cistern for Bank Exams Exam

A funnel can discharge a tank in 40 minutes. A second pipe with distance across twice as much as that of the first is likewise joined with the tank to purge it. The two together can exhaust the tank in:
  • a)
    8 min
  • b)
    40/3 min
  • c)
    30 min
  • d)
    38 min
Correct answer is option 'B'. Can you explain this answer?

Understanding the Problem
To determine how long it takes for two pipes to discharge a tank together, we start with the information given:
- A funnel discharges the tank in 40 minutes.
- A second pipe has a distance across twice as much as the first.
Calculating Individual Rates
- The rate of the first pipe (funnel) is:
Rate1 = 1 tank / 40 min = 1/40 tanks per minute.
- The second pipe is not explicitly given a discharge time, but since it’s twice the distance, we can assume it discharges at half the rate of the first pipe.
Rate2 = 1/80 tanks per minute (since it takes twice as long due to the greater distance).
Combined Rate of Both Pipes
To find out how quickly both pipes can discharge the tank together, we add their rates:
- Combined Rate = Rate1 + Rate2
Combined Rate = (1/40 + 1/80) tanks per minute.
To add these fractions, we find a common denominator (which is 80):
- Combined Rate = (2/80 + 1/80) = 3/80 tanks per minute.
Time Taken to Discharge the Tank
Now, to find the time taken to discharge 1 tank using the combined rate:
- Time = 1 tank / (3/80 tanks per minute)
- Time = 80/3 minutes.
Thus, the two pipes together can exhaust the tank in 80/3 minutes, which is approximately 26.67 minutes.
Conclusion
The correct answer is option 'B': 40/3 minutes. This matches our calculated result, confirming that the combined effort of both pipes significantly reduces the time taken to discharge the tank.

A tank can be filled by pipe A in 2 hours and pipe B in 6 hours. At 10 A.M. pipe A was opened. At what time will the tank be filled if pipe B is opened at 11 A.M.?
  • a)
    12 P.M.
  • b)
    12.45 A.M.
  • c)
    5 P.M
  • d)
    11.45 A.M.
Correct answer is option 'D'. Can you explain this answer?

Part of the tank filled in 1 hour by pipe A = 1/2
Part of the tank filled by both pipes in1 hour

So, Time taken to fill 2/3 part = 60 minutes
Time taken to fill 1/2 part

The tank will be filled at 11:45 A.M.

If two pipes function simultaneously, a tank is filled in 12 hours. One pipe fills the tank 10 hours faster than the other. How many hours does the faster pipe alone take to fill the tank?
  • a)
    12 hrs
  • b)
    20 hrs
  • c)
    18 hrs
  • d)
    15 hrs
Correct answer is option 'B'. Can you explain this answer?

Malavika Rane answered
Understanding the Problem
To tackle the problem, let's define the variables and the relationships between the pipes.
- Let the time taken by the slower pipe to fill the tank be \( x \) hours.
- Then, the faster pipe will take \( x - 10 \) hours to fill the tank.
Working Together
When both pipes work together, they fill the tank in 12 hours. The rates of filling for each pipe are:
- Slower pipe: \( \frac{1}{x} \) (tank per hour)
- Faster pipe: \( \frac{1}{x - 10} \) (tank per hour)
The combined rate of both pipes working together is:
\[ \frac{1}{x} + \frac{1}{x - 10} = \frac{1}{12} \]
Setting Up the Equation
To find \( x \), we can combine the fractions:
\[ \frac{(x - 10) + x}{x(x - 10)} = \frac{1}{12} \]
This simplifies to:
\[ \frac{2x - 10}{x^2 - 10x} = \frac{1}{12} \]
Cross-multiplying gives:
\[ 12(2x - 10) = x^2 - 10x \]
Expanding and rearranging results in:
\[ x^2 - 34x + 120 = 0 \]
Solving the Quadratic Equation
Now, we can solve this quadratic equation using the quadratic formula:
\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \]
Where \( a = 1, b = -34, c = 120 \):
- Discriminant: \( b^2 - 4ac = 1156 - 480 = 676 \)
- Roots:
\[ x = \frac{34 \pm 26}{2} \]
Calculating gives:
- \( x = 30 \) (slower pipe)
- \( x = 4 \) (not valid since it must be greater than 10)
Therefore, the slower pipe takes 30 hours, and the faster pipe takes:
\[ x - 10 = 30 - 10 = 20 \text{ hours} \]
Conclusion
The faster pipe alone takes 20 hours to fill the tank, confirming the correct answer is option B.

Two channels can fill a tank in 15 hours and 12 hours separately and a third pipe can purge it in 4 hours. In the event that the channels are opened all together at 8 am, 9 am and 11am separately, the tank will be exhausted at
  • a)
    11.40 am
  • b)
    12.40 pm
  • c)
    1.40 pm
  • d)
    2.40 pm
Correct answer is option 'D'. Can you explain this answer?

Arnav Saini answered
Given Data:
- First channel fills the tank in 15 hours
- Second channel fills the tank in 12 hours
- Third pipe empties the tank in 4 hours

Approach:
- Find the filling rate per hour for each channel
- Calculate the net filling rate when all channels are opened simultaneously
- Determine the time taken to empty the tank

Calculations:
- Filling rate for first channel = 1/15 tank/hour
- Filling rate for second channel = 1/12 tank/hour
- Emptying rate for third pipe = 1/4 tank/hour
- Combined filling rate = 1/15 + 1/12 - 1/4 = 1/20 tank/hour
- Time taken to empty the tank with the combined rate = 1 / (1/20) = 20 hours
- Channels opened at 8 am, 9 am, and 11 am respectively
- Tank will be emptied at 8 am + 20 hours = 4 pm

Final Answer:
- The tank will be emptied at 4.00 pm (Option D)

Three taps A,B and C together can fill an empty cistern in 10 minutes. The tap A alone can fill it in 30 minutes and the tap B alone in 40 minutes. How long will the tap C alone take to fill it ?
  • a)
    40 minutes
  • b)
    16 minutes
  • c)
    24 minutes
  • d)
    32 minutes
Correct answer is option 'C'. Can you explain this answer?

Ishaan Roy answered
Understanding the Problem
We have three taps A, B, and C which can fill a cistern in different times. We need to find out how long tap C takes to fill the cistern alone.
Given Information
- All taps together (A, B, C) can fill the cistern in 10 minutes.
- Tap A alone can fill the cistern in 30 minutes.
- Tap B alone can fill the cistern in 40 minutes.
Filling Rates Calculation
- Rate of Tap A:
A fills 1/30 of the cistern per minute.
- Rate of Tap B:
B fills 1/40 of the cistern per minute.
- Rate of Tap C:
Let the rate of tap C be 1/x of the cistern per minute.
- Combined Rate:
Together, A, B, and C fill 1/10 of the cistern per minute.
Setting Up the Equation
We can set up the equation based on their combined rates:
(1/30) + (1/40) + (1/x) = 1/10
Finding a Common Denominator
- The least common multiple of 30, 40, and 10 is 120.
- Convert each rate to have a denominator of 120:
- (1/30) = 4/120
- (1/40) = 3/120
- (1/10) = 12/120
Now we can rewrite the equation:
4/120 + 3/120 + 1/x = 12/120
Solving for Tap C's Rate
- Combine the fractions:
(4 + 3)/120 + 1/x = 12/120
7/120 + 1/x = 12/120
- Rearranging gives us:
1/x = 12/120 - 7/120
1/x = 5/120
- Therefore, x = 24 minutes.
Conclusion
Thus, tap C alone will take 24 minutes to fill the cistern. The correct answer is option 'C'.

A break in the base of a tank can purge the full tank in 6 hours. A channel funnel fills water at the rate of 4 liters for each moment. At the point when the tank is full, the channel is opened and because of the break, the tank is void in 8 hours. The limit of the tank is
  • a)
    5260 ltr.
  • b)
    5760 ltr.
  • c)
    5846 ltr.
  • d)
    6970 ltr.
Correct answer is option 'B'. Can you explain this answer?

Arnav Saini answered
Given Data:
- Time taken to empty the tank with the break in the base: 6 hours
- Rate at which the channel funnel fills water: 4 liters per minute
- Time taken to empty the tank with the break in 8 hours

Calculating the Capacity of the Tank:
- Let the capacity of the tank be x liters.
- The tank is emptied in 6 hours with the break, so the leak rate = x/6 liters per hour
- The tank is filled by the channel funnel at a rate of 4 liters per minute = 240 liters per hour
- The net outflow rate due to the leak = 240 - x/6 liters per hour
- The tank is emptied in 8 hours, so the total outflow rate = x/8 liters per hour
- Equating the two outflow rates:
x/8 = 240 - x/6
Solving the above equation, we get x = 5760 liters
Therefore, the capacity of the tank is 5760 liters. Option B is the correct answer.

A tap can fill storage in 8 hours and another tap can discharge it in 16 hours. In the event that both the taps are open, the time taken to fill the tank will be:
  • a)
    8 hours
  • b)
    10 hours
  • c)
    16 hours
  • d)
    24 hours
Correct answer is option 'C'. Can you explain this answer?

Ishaan Roy answered
Understanding the Problem
In this scenario, we have two taps: one that fills a tank and another that empties it.
Details of the Taps
- Filling Tap: Fills the tank in 8 hours.
- Discharging Tap: Empties the tank in 16 hours.
Calculating Rates of Work
- Filling Rate: The filling tap can fill 1 tank in 8 hours, which means it fills 1/8 of the tank in one hour.
- Discharging Rate: The discharging tap can empty 1 tank in 16 hours, meaning it empties 1/16 of the tank in one hour.
Combined Rate of Work
To find the combined effect of both taps working together, we add their rates:
- Net Filling Rate = Filling Rate - Discharging Rate
- Net Filling Rate = 1/8 - 1/16
Finding a Common Denominator
To perform this operation, we convert the fractions:
- 1/8 = 2/16
Now we can subtract:
- Net Filling Rate = 2/16 - 1/16 = 1/16
Time Taken to Fill the Tank
To find the time taken to fill the tank when both taps are open:
- If the net filling rate is 1/16 of the tank per hour, it will take 16 hours to fill 1 full tank.
Final Conclusion
Thus, when both taps are open, the time taken to fill the tank is 16 hours, confirming that option 'C' is correct.

A cistern has 3 pipes A, B and C. A and B can ill it in 3 hours and 4 hours respectively while C can empty the completely filled cistern in 1 hour. If the pipes are opened in order at 3, 4 and 5 pm respectively, at what time will the cistern be empty?
  • a)
    7:12 PM
  • b)
    6:15 PM
  • c)
    8:12 PM
  • d)
    8:35 PM
Correct answer is option 'A'. Can you explain this answer?

Understanding the Problem
To solve the problem, we need to analyze the rates at which the pipes fill or empty the cistern and their operational timings.
Pipe Rates
- Pipe A can fill the cistern in 3 hours, so its rate is 1/3 of the cistern per hour.
- Pipe B can fill the cistern in 4 hours, so its rate is 1/4 of the cistern per hour.
- Pipe C can empty the cistern in 1 hour, so its rate is -1 (emptying) per hour.
Combined Rates of A and B
- When A and B are opened together:
- Rate of A + Rate of B = 1/3 + 1/4 = 4/12 + 3/12 = 7/12 of the cistern per hour.
Operational Sequence
- At 3 PM:
- Only Pipe A is open.
- In 1 hour (from 3 PM to 4 PM), it fills 1/3 of the cistern.
- At 4 PM:
- Pipes A and B are open.
- They fill together at a rate of 7/12 of the cistern per hour.
- From 4 PM to 5 PM (1 hour), they fill 7/12 of the cistern.
- Total filled by 5 PM: 1/3 + 7/12 = 4/12 + 7/12 = 11/12 of the cistern.
- At 5 PM:
- All pipes A, B, and C are open.
- The combined rate is (7/12 - 1) = 7/12 - 12/12 = -5/12 (emptying at this rate).
Time to Empty the Cistern
- From 5 PM, 1/12 of the cistern remains.
- Time taken to empty 1/12 at -5/12 rate = (1/12) / (5/12) = 1/5 hours = 12 minutes.
Final Calculation
- 5 PM + 12 minutes = 5:12 PM.
- Therefore, the cistern will be empty by 7:12 PM.
Thus, the correct answer is option 'A': 7:12 PM.

Two pipes can fill a cistern separately in 10 hours and 15 hours. They can together fill the cistern in
  • a)
    9 hours
  • b)
    6 hours
  • c)
    7 hours
  • d)
    8 hours
Correct answer is option 'B'. Can you explain this answer?

Abhiram Mehra answered
Understanding the Problem
To solve the problem of how long two pipes can fill a cistern together, we start by determining their individual filling rates.
Individual Filling Rates
- Pipe A can fill the cistern in 10 hours. Therefore, its rate is 1/10 cisterns per hour.
- Pipe B can fill the cistern in 15 hours. Hence, its rate is 1/15 cisterns per hour.
Combined Filling Rate
To find the combined rate of both pipes, we add their individual rates:
- Combined rate = Rate of Pipe A + Rate of Pipe B
- Combined rate = 1/10 + 1/15
To perform this addition, we need a common denominator. The least common multiple of 10 and 15 is 30.
- 1/10 = 3/30
- 1/15 = 2/30
Now, adding these rates:
- Combined rate = 3/30 + 2/30 = 5/30 = 1/6
Time to Fill the Cistern Together
The combined rate of 1/6 means that together, the two pipes can fill 1 cistern in 6 hours.
Conclusion
The correct answer is option 'B', as the two pipes working together can fill the cistern in 6 hours.

A tap can fill a cistern in 8 hours and another tap can empty it in 16 hours. If both the taps are open, the time (in hours) taken to fill the tank will be :
  • a)
    24
  • b)
    8
  • c)
    10
  • d)
    16
Correct answer is option 'D'. Can you explain this answer?

Ssc Cgl answered
Part of the cistern filled in 1 hour = 1/8
Part of the cistern emptied in 1 hour = 1/16
When both the taps are opened simultaneously, part of cistern filled in 1 hour

Hence, the cistern will be filled in 16 hours.
Using Rule 7,
Here, x = 8, y = 16
Required time 

Three pipes P, Q and R can separately fill a cistern in 4,8 and 12 hours respectively. Another pipe S can empty the completely filled cistern in10 hours. Which of the following arrangements will fill the empty cistern in less time than others ?
  • a)
    P, Q and S are open.
  • b)
    Q alone is open.
  • c)
    P and S are open.
  • d)
    P, R and S are open.
Correct answer is option 'A'. Can you explain this answer?

EduRev SSC CGL answered
Using Rule 2 and 7,
Part of the cistern filled in 1 hour
when pipes P and S are open

Hence, the cistern will be filled in 20/3 hours ≈ 6.6 hours
Part of the cistern filled in 1 hour
when pipes P, R and S are open

Hence, the cistern will be filled in 30/7 hours ≈ 4.3 hours
Part of the cistern filled in I hour
when pipes P, Q and S are open

Hence, the cistern will be filled in 40/11 hours ≈ 3.6 hours
Cistern can be filled faster when P, Q & S are open

A tank is fitted with two taps A and B. A can fill the tank totally in 45 minutes and B can purge the full tank in 60 minutes. On the off chance that both the taps are opened on the other hand for 1 minute, then in what amount of time the unfilled tank will be filled totally?
  • a)
    2 hrs 55 min
  • b)
    3 hrs 40 min
  • c)
    5 hrs 53 min
  • d)
    none of these
Correct answer is option 'D'. Can you explain this answer?

Work done by A in 1st minutes and B 2nd minute = (1/45- 1/60)= 1/180
Part filled in 2 min = 1/180
Part filled in 358 min = (1/360*358) =  358/360 = 179/180
Remaining part = (1-179/180) = 1/180
1/45 part is filled by A in (45*1/180) min= 1/4 min.
Total time taken to fill it = 358 1/4 min = 5 hrs.58 min 15 sec.

Two pipes A and B can fill a tank in 36 minutes and 45 minutes respectively. Another pipe C can empty the tank in 30 minutes. First A and B are opened. After 7 minutes, C is also opened. The tank is filled up in
  • a)
    45 minutes
  • b)
    39 minutes
  • c)
    46 minutes
  • d)
    40 minutes
Correct answer is option 'C'. Can you explain this answer?

Ssc Cgl answered
Part of the tank filled by pipes A and B in 1 minute

Part of the tank filled by these pipes in 7 minutes
= 7/20
Remaining unfilled part

When all three pipes are opened.

Time taken in filling 13/20 part

Required time = 39 + 7 = 46 minutes

Two pipes A and B can fill a water tank in 20 and 24 min respectively. A third pipe C can empty at the rate of 3 gallons per minute. If A, B and C opened together fill the tank in 15 min, the capacity of the tank (in gallons) is:
  • a)
    180
  • b)
    150
  • c)
    120
  • d)
    60
Correct answer is option 'C'. Can you explain this answer?

Let the capacity of the tank = x gallons
Quantity of the water filled in the tank in 1 min when all the pipes A, B and C are opened simultaneously= x/20 + x/24 - 3
According to question,
x/20 + x/24 - 3 = x/15
or, x/20 + x/24 - x/15 = 3
or, (6x + 5x  - 8x)/120 = 3
or, 3x/120 = 3
or, x = 120 gallons

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