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Question

Three pipes A, B and C can fill a tank in 12 hours, 18 hours and 24 hours, respectively. A leak at the bottom can empty the full tank in 36 hours. If all the pipes are opened together, in how many hours will the tank be filled? (Round off your answer to two decimal places.)

This question was previously asked in
RRB ALP 2025 CBT 2 Wiremen Question Paper (28-Jul-2026) (Shift 2)
The correct answer is

6.55 hours

To find out how long it will take to fill the tank with all the pipes and the leak working together, we need to determine the net rate at which the tank fills. Let's calculate this step by step:

  1. The rate at which pipe A fills the tank is \( \frac{1}{12} \) of the tank per hour because it can fill the entire tank in 12 hours.
  2. Similarly, the rate at which pipe B fills the tank is \( \frac{1}{18} \) of the tank per hour.
  3. And pipe C fills the tank at a rate of \( \frac{1}{24} \) of the tank per hour.
  4. The leak, which empties the tank, works at a rate of \( \frac{1}{36} \) of the tank per hour.
  5. To find the net rate of filling the tank, we add the rates of pipes A, B, and C and subtract the rate at which the leak empties the tank. The equation is given by: \(\text{Net rate} = \left(\frac{1}{12} + \frac{1}{18} + \frac{1}{24}\right) - \frac{1}{36}\)
  6. Calculating each part:
    • \( \frac{1}{12} = 0.0833 \) (approx.)
    • \( \frac{1}{18} = 0.0556 \) (approx.)
    • \( \frac{1}{24} = 0.0417 \) (approx.)
    • \( \frac{1}{36} = 0.0278 \) (approx.)
  7. Add these rates: \(0.0833 + 0.0556 + 0.0417 - 0.0278 = 0.1528\)
  8. Therefore, the net rate at which the tank is filled is \( 0.1528 \) of the tank per hour.
  9. To find the total time required to fill one tank, we calculate the reciprocal of the net rate: \(\text{Time} = \frac{1}{0.1528} \approx 6.55 \text{ hours}\)

Hence, the time taken to fill the tank with all the pipes working along with the leak is approximately 6.55 hours. Therefore, the correct answer is 6.55 hours.

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Similar Questions

  1. Two pipes A and B can fill an empty cistern in 32 and 48 hours, respectively. Pipe C can drain the entire cistern in 64 hours when no other pipe is in operation. Initially, when the cistern was empty Pipe A and Pipe C were turned on. After a few hours, Pipe A was turned off and Pipe B was turned on instantly. In all it took 112 hours to fill the cistern. For how many hours was Pipe B turned on?

  2. One pipe can fill an empty cistern in 4 hours while another can drain the cistern when full in 10 hours. Both the pipes were turned on when the cistern was half-empty. How long will it take the cistern to be full?

  3. One of the two inlet pipes works twice as efficiently as the other. The two, working alongside a drain pipe that can empty a cistern all by itself in 8 hours, can fill the empty cistern in 8 hours. How many hours will the less efficient inlet pipe take to fill the empty cistern by itself?

  4. Two pipes, when working one at a time can fill a cistern in 2 hours and 3 hours, respectively while a third pipe can drain the cistern empty in 6 hours. All the three pipes were opened together when the cistern was 1/6 full. How long will it take for the cistern to be completely full?

  5. A tanker can fill a cistern in 12 hours. After half the cistern is filled, 2 more similar tankers are opened. What is the time taken to fill the remaining half of the tank?

  6. A sump is filled by three tankers with uniform flow. The first two tankers operating simultaneously fill the sump in the same time during which the sump is filled by the third tanker alone. The second tanker fills the sump 5 hours faster than the first tanker and 4 hours slower than the third tanker. The time required by the first tanker is:

  7. Two pipes fill a tank when working individually in 25 and 40 hours, respectively while a third pipe can drain the filled tank in 16 hours. If all the three pipes are turned on at the same time when the tank is empty, how long will it take to fill the tank completely?
  8. Pipe A can fill a tank in 12 hours. Pipe B can empty it in X hours. If both the pipes are opened together, then the tank will be filled in 30 hours. Find X.

  9. Pipe A can fill an empty cistern in 6 hours while along with Pipe B it can fill it up in 4 hours. Only Pipe B is on for an hour after which Pipe A is also turned on. How much time will it take in all to fill up the cistern?
  10. 15 pipes, each having the same diameter, can fill a cistern in 12 minutes. How long will it take for 6 pipes, each with double the original diameter, to fill the same cistern at the same speed of the flow?


Important Questions from Pipe and Cistern

  1. Two pipes A and B can independently fill a tank completely in 20 and 30 minutes respectively. If both the pipes are opened simultaneously, how much time will they take to fill the tank completely?

  2. The compound interest on Rs. 64,000 for 3 years, compounded annually at 7.5% p.a. is

  3. A water tank can be emptied in 40 minutes by a pipe of d 'diameter, so how long will it take for a 2d diameter pipe to be emptied?

  4. Two pipes X and Y can fill an empty tank in 16 hours and 20 hours respectively. Pipe Z alone can empty the completely filled tank in 25 hours. Firstly both pipes X and Y are opened and after 6 hours pipe Z is also opened. What will be the total time (in hours) taken to completely fill the tank?

  5. Pipe J can fill a tank in 48 hours and pipe K can fill the same tank in 72 hours. If both the pipes are opened alternately for one hour each and pipe K is opened for the first hour, then in how much time the tank will be full?

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