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Pipe A can fill a tank in 4 hours, pipe B can fill the same tank in 6 hours and pipe C can fill the same tank in 12 hours. The time taken (in hours) by them to fill half of the same tank if they operate together is:

This question was previously asked in
RRB Group D 2025 Question Paper (18-Aug-2026) (Shift 1)
The correct answer is

1

Combined rate of the three pipes filling together \(= \dfrac{1}{4} + \dfrac{1}{6} + \dfrac{1}{12}\) tank per hour.

Taking LCM 12: \(\dfrac{3}{12} + \dfrac{2}{12} + \dfrac{1}{12} = \dfrac{6}{12} = \dfrac{1}{2}\) tank per hour.

So together they fill the full tank in \(2\) hours.

Time to fill half the tank \(= \dfrac{1}{2} \times 2 = 1\) hour.

Hence, the three pipes together take 1 hour to fill half of the tank.

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Similar Questions

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  2. One pipe can fill a tank in 6 minutes, while another pipe can empty the completely filled tank in 9 minutes. If both the pipes are opened together when the tank is empty, how many minutes will it take to fill one-half of the tank?

  3. P and Q together can fill a cistern with water in 15 hours. If P alone can fill the cistern with water in 60 hours, then in how many hours will Q alone fill one-fourth of the same cistern with water?

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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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