What is pipe and cistern concept about?

This topic involves filling or emptying a tank using pipes. Inlet fills the tank as positive work and outlet empties it as negative work. The concept is exactly the same as Time and Work where pipes act as workers. Asked in CAT, SSC CGL, Bank PO and Railway exams.

Pipe and Cistern Concept | 5 Key Formulas, Tricks and Solved Examples

Pipe and cistern is an important and frequently tested topic in quantitative aptitude for competitive exams. It is asked in almost every major exam including CAT, SSC CGL, SSC CHSL, Bank PO, Bank Clerk, Railway RRB and CSAT. A strong understanding of pipe and cistern concept, formulas and tricks is essential for scoring well in these exams. The concept used in pipe and cistern problems is exactly the same as the concept used in time and work — where inlet pipes act as workers filling the tank and outlet pipes act as workers emptying the tank. In this post we cover everything from inlet pipe and outlet pipe definition, filling and emptying time formula, LCM method for solving pipe and cistern problems, problems when multiple pipes are opened and closed in between — all explained with clear formulas and solved examples.

📚 What You Will Learn in This Post

What is Pipe and Cistern — Inlet Pipe and Outlet Pipe Definition

Filling Time Formula — LCM Method for Pipe and Cistern

Emptying Time Formula — Outlet Pipe Problems

Multiple Pipes Opened Together — Combined Efficiency Formula

Pipes Opened and Closed in Between — Formula and Examples

Relation Between Pipe and Cistern and Time and Work Concept

Pipe & Cistern
Concept:

In this chapter to solve problems of pipe and cistern the concept used is very same to the concept used in chapter of Time & Work.

Pipe and cistern is an important topic in quantitative aptitude asked in CAT, SSC CGL, SSC CHSL, Bank PO, Bank Clerk, Railway RRB and CSAT. The concept used in pipe and cistern problems is exactly the same as the concept used in Time and Work. An inlet pipe that fills a tank works exactly like a worker doing positive work and an outlet pipe that empties a tank works exactly like a worker doing negative work. The tank capacity is equivalent to total work to be done.

For complete formulas, shortcut tricks, LCM method and solved examples please refer to our detailed Time and Work Concept page — all methods explained there apply directly to pipe and cistern problems. Pipe and cistern is a well known topic in fluid dynamics and is one of the most frequently asked topics in quantitative aptitude for competitive exams.

📌 Key Points to Remember

Inlet Pipe — Fills the tank — Positive work — Same as worker joining

Outlet Pipe — Empties the tank — Negative work — S

❓ Frequently Asked Questions

Q1. What is this concept about?

This topic involves filling or emptying a tank using pipes. An inlet fills the tank and is treated as positive work. An outlet empties the tank and is treated as negative work. The concept is exactly the same as Time and Work where pipes act as workers. This topic is asked in CAT, SSC CGL, Bank PO and Railway exams.

Q2. What is an inlet pipe and outlet pipe?

An inlet fills the cistern and does positive work. An outlet empties the cistern and does negative work. When both are open simultaneously net work per unit time = efficiency of inlet minus efficiency of outlet.

Q3. How to solve these problems using LCM method?

Take total capacity as LCM of individual times. Efficiency of each = Total Capacity divided by its time. Inlet efficiency is positive and outlet efficiency is negative. Net efficiency = sum of all. Filling time = Total Capacity divided by Net Efficiency.

Q4. What happens when an inlet and outlet are opened together?

When inlet fills in A hours and outlet empties in B hours and both are open then net filling time = AB divided by (B minus A) when A is less than B. If A is greater than B the tank will never fill and will be emptied instead.

Q5. How to solve problems when pipes are opened and closed alternately?

Calculate work done in each cycle of opening and closing. Find how many complete cycles are needed then calculate remaining work. This is similar to time and work problems where workers join and leave alternately.

Q6. What is the relation with Time and Work concept?

Inlet = positive work, outlet = negative work, tank capacity = total work. All LCM method formulas and efficiency rules from Time and Work directly apply here.

Q7. Which competitive exams cover this topic?

This topic is asked in CAT, SSC CGL, SSC CHSL, Bank PO, Bank Clerk, Railway RRB, CSAT and all state level competitive exams. Mastering it together with Time and Work gives a significant advantage in exams.

Q8. Where can I practice questions on this topic?

You can practice on our Pipe and Cistern Exercise page which contains solved practice questions covering all types of problems asked in competitive exams.

Pipe and Cistern Concept — Formula, Tricks and Solved Examples

📚 What You Will Learn in This Post

📌 Key Points to Remember

❓ Frequently Asked Questions

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