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UPSSSC PETQuestion 11 of 11 · Pipes & Cisterns
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UPSSSC PET 2023 (28 Oct Shift 1)

Directions

There are five inlet pipes (A, B, C, D and E) and five outlet pipes (P, Q, R, S and T) connected to a tank. The first pie-chart represents the percentage of the tank filled by each inlet pipe when all the inlet pipes are opened together and the second pie-chart represents the percentage of the tank emptied by each outlet pipe when all the outlet pipes are opened together. Total capacity of the tank = 1000 litres; Time taken to fill the tank when all the inlet pipes are opened together = 2 minutes; Time taken to empty the tank when all the outlet pipes are opened together = 1.6 minutes. figure

If all the inlet pipes and the outlet pipes are opened together then find the time taken to empty the full tank.

Answer View answer ▾

Answer: Option A — 8 minutes

Detailed Solution

1

All inlets fill 500 litres/min and all outlets empty 625 litres/min, so the net outflow litres/min.

2

Time to empty the full tank minutes.

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More Pipes & Cisterns Questions

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  1. Q1.Pipe A can fill a tank in 12 hours and pipe B can fill it in 15 hours. If both pipes are opened together, the tank will be filled in
  2. Q2.A pipe can fill a tank in 10 hours and an outlet pipe can empty the full tank in 15 hours. If both are opened together on an empty tank, the tank will be full in
  3. Q3.Pipes A and B can fill a tank in 20 minutes and 30 minutes respectively. Both are opened together, and after 6 minutes pipe A is closed. How much more time will B take to fill the tank?
  4. Q4.Three pipes A, B and C can fill a tank in 6 hours, 8 hours and 12 hours respectively. If all three are opened together, the tank will be filled in
  5. Q5.A pipe can fill a tank in 8 hours. Because of a leak at the bottom, it takes 10 hours to fill the tank. In how many hours can the leak alone empty the full tank?

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Pipes & Cisterns — UPSSSC PET Preparation

This question tests your understanding of Pipes & Cisterns, a key topic in the UPSSSC PET Quantitative Aptitude section. The detailed solution above uses a step-by-step approach to show the reasoning, and where available, a shortcut that helps you solve similar questions in under 90 seconds during the actual exam.

Pipes and cisterns questions are an application of time and work. An inlet pipe fills a tank and does positive work, while an outlet pipe or leak empties it and does negative work. If an inlet pipe fills a tank in a hours, it fills 1/a of the tank each hour. If an outlet pipe empties it in b hours, it removes 1/b each hour. Questions involve several pipes opened together, pipes opened or closed partway through, leaks that slow down filling, and pipes with different filling rates. The LCM method works especially well. Take the tank's capacity as the LCM of the given times, find each pipe's rate in units per hour (negative for outlet pipes and leaks), and add the rates. This avoids fractions entirely. Always check whether the question asks for the time to fill or the time to empty. Practise the pipes and cisterns questions below, each with a step-by-step solution using the LCM method.

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