# Pipes and Cistern Question & Answers

## Pipes and Cisterns

Quantitative aptitude questions are asked in many competitive exams and placement exam. 'Pipes and Cisterns' is a category in Quantitative Aptitude. Quantitative aptitude questions given here are extremely useful for all kind of competitive exams like Common Aptitude Test (CAT), MAT, GMAT, IBPS Exam, CSAT, CLAT, Bank Competitive Exams, ICET, UPSC Competitive Exams, CLAT, SSC Competitive Exams, SNAP Test, KPSC, XAT, GRE, Defense Competitive Exams, L.I.C/ G. I.C Competitive Exams, Railway Competitive Exam, TNPSC, University Grants Commission (UGC), Career Aptitude Test (IT Companies) and etc., Government Exams etc.

We have a large database of problems on "Pipes and Cisterns" answered with explanation. These will help students who are preparing for all types of competitive examinations.

Two pipes A and B can fill a tank in 15 minutes and 20 minutes respectively. Both the pipes are opened together but after 4 minutes, pipe A is turned off. What is the total time required to fill the tank?

 A) 10 min. 20 sec. B) 11 min. 45 sec. C) 12 min. 30 sec. D) 14 min. 40 sec.

Explanation:

Part filled in 4 minutes =${\color{Black}&space;4\left&space;(&space;\frac{1}{15}+\frac{1}{20}&space;\right&space;)=\frac{7}{15}}$

Remaining part =${\color{Black}&space;\left&space;(&space;1-\frac{7}{15}&space;\right&space;)=\frac{8}{15}}$

Part filled by B in 1 minute =${\color{Black}&space;\frac{1}{20}}$

${\color{Black}\therefore&space;\frac{1}{20}:\frac{8}{15}::1:x}$

${\color{Black}x=\left&space;(&space;\frac{8}{15}&space;\times&space;1\times&space;20\right&space;)=10\frac{2}{3}min=10min.40sec.}$

${\color{Black}&space;\therefore&space;}$The tank will be full in (4 min. + 10 min. + 40 sec.) = 14 min. 40 sec

Subject: Pipes and Cistern - Quantitative Aptitude - Arithmetic Ability

15

Three pipes A, B and C can fill a tank in 6 hours. After working at it together for 2 hours, C is closed and A and B can fill the remaining part in 7 hours. The number of hours taken by C alone to fill the tank is:

 A) 10 B) 12 C) 14 D) 16

Explanation:

Part filled in 2 hours =${\color{Black}&space;\frac{2}{6}=\frac{1}{3}}$

Remaining part =${\color{Black}&space;\left&space;(&space;1-\frac{1}{3}&space;\right&space;)=\frac{2}{3}}$

${\color{Black}&space;\therefore&space;}$ (A + B)'s 7 hour's work =${\color{Black}&space;\frac{2}{3}}$

(A + B)'s 1 hour's work =${\color{Black}&space;\frac{2}{21}}$

${\color{Black}&space;}$${\color{Black}\therefore&space;}$C's 1 hour's work = { (A + B + C)'s 1 hour's work } - { (A + B)'s 1 hour's work }

=${\color{Black}&space;\left&space;(&space;\frac{1}{6}-\frac{2}{21}&space;\right&space;)=\frac{1}{14}}$

${\color{Black}&space;\therefore&space;}$C alone can fill the tank in 14 hours.

Subject: Pipes and Cistern - Quantitative Aptitude - Arithmetic Ability

9

A tap can fill a tank in 6 hours. After half the tank is filled, three more similar taps are opened. What is the total time taken to fill the tank completely?

 A) 3 hrs 15 min B) 3 hrs 45 min C) 4 hrs 15 min D) 4 hrs 1

Explanation:

Time taken by one tap to fill half of the tank = 3 hrs.

Part filled by the four taps in 1 hour =${\color{Black}&space;\left&space;(&space;4\times&space;\frac{1}{6}&space;\right&space;)=\frac{2}{3}}$

Remaining part =${\color{Black}&space;\left&space;(&space;1-&space;\frac{1}{2}&space;\right&space;)=\frac{1}{2}}$

${\color{Black}&space;\therefore&space;\frac{2}{3}:\frac{1}{2}&space;::1:x}$

${\color{Black}&space;\Rightarrow&space;x=\left&space;(&space;\frac{1}{2}&space;\times&space;1\times&space;\frac{3}{2}\right&space;)=\frac{3}{4}}$

So, total time taken = 3 hrs. 45 mins.

Subject: Pipes and Cistern - Quantitative Aptitude - Arithmetic Ability

7

A booster pump can be used for filling as well as for emptying a tank. The capacity of the tank is 2400 ${\color{Blue} m^{3}}$. The emptying capacity of the tank is 10 $\inline {\color{Blue} m^{3}}$ per minute heigher than its filling capacity and the pump needs 8 minutes lesser to empty the tank than it needs to fill it. What is the filling capacity of the pump?

 A) 50 m^3/min B) 60 m^3/min C) 72 m^3/min D) None of these

Explanation:

Let the filling capacity of the pump be x $\inline {\color{Black} m^{3}}$/min.

Then, emptying capacity of the pump=(x+10) $\inline {\color{Black} m^{3}}$/min.

so,$\inline {\color{Black} \frac{2400}{x}-\frac{2400}{x+10}=8\; \; \Leftrightarrow x^{2}+10x-3000=0}$

$\inline {\color{Black} \Leftrightarrow \left ( x-50 \right )+\left ( x+60 \right )=0\; \; \Leftrightarrow x=50}$

Subject: Pipes and Cistern - Quantitative Aptitude - Arithmetic Ability

11

A pump can fill a tank with water in 2 hours. Because of a leak, it took $\inline \fn_jvn 2\frac{1}{3}$ hours to fill the tank. The leak can drain all the water of the tank in:

 A) 7 hours B) 8 hours C) 12 hours D) 14 hours

Work done by the leak in 1 hour =${\color{Black}&space;\left&space;(&space;\frac{1}{2}-\frac{3}{7}&space;\right&space;)=\frac{1}{14}}$
${\color{Black}&space;\therefore&space;}$ Leak will empty the tank in 14 hrs