Pipes And Cistern(Quantitative Aptitude ) Questions and answers for exam Preparation

Quantitative Aptitude

PIPES AND CISTERN MCQs

Pipes & Cisterns

Total Questions : 431 | Page 38 of 44 pages

Question 371. A tank is fitted with two taps. The first tap can fill the tank completely in 45 minutes and the second tap can empty the full tank in one hour. If both the taps are opened alternately for one minute, then in how many hours the empty tank will be filled completely ?

5 hours 53 minutes
4 hours 48 minutes
2 hours 55 minutes
3 hours 40 minutes

Discuss Question

Answer: Option A. -> 5 hours 53 minutes
Answer: (a)Using Rule 7,Part of the tank filled in one minute= $1/45 - 1/60 = {4 - 3}/180 = 1/180$Since, $1/180$ part is filled in 1 minute$1 - 1/45 = 44/45$ part is filled in${2 × 180 × 44}/45$ = 352 minutesi.e. 5 hours 52 minutesRemaining $1/45$ part will be filled in 1 minute.Total time taken = 5 hours 53 minutes

Question 372. A pipe can fill a cistern in 9 hours. Due to a leak in its bottom, the cistern fills up in 10 hours. If the cistern is full, in how much time will it be emptied by the leak ?

100 hours
90 hours
70 hours
80 hours

Discuss Question

Answer: Option B. -> 90 hours
Answer: (b)Using Rule 7,Part of the tank emptied by the leak in 1 hour= $1/9 - 1/10 = {10 - 9}/90 = 1/90$Required time = 90 hours

Question 373. A pipe can fill a tank in 24 hrs. Due to a leakage in the bottom, it is filled in 36 hrs. If the tank is half full, how much time will the leak take to empty the tank?

24 hrs
36 hrs
48 hrs
72 hrs

Discuss Question

Answer: Option B. -> 36 hrs
Answer: (b)Using Rule 7,Part of tank emptied by leak in an hour= $1/36 - 1/24 = {2 - 3}/72 = {–1}/72$Time taken in emptying the full tank= 72 hoursRequired time = 36 hours

Question 374. A cistern is normally filled in 8 hours but takes another 2 hours longer to fill because of a leak in its bottom. If the cistern is full, the leak will empty it in :

40 hours
25 hours
16 hours
20 hours

Discuss Question

Answer: Option A. -> 40 hours
Answer: (a)Using Rule 7,Part emptied by the leak in 1 hour= $1/8 - 1/10 = {5 - 4}/40 = 1/40$The leak will empty the cistern in 40 hours.

Question 375. A tap can fill a cistern in 40 minutes and a second tap can empty the filled cistern in 60 minutes. By mistake without closing the second tap, the first tap was opened. In how many minutes will the empty cistern be filled ?

Discuss Question

Answer: Option A. -> 120
Answer: (a)Using Rule 7,Tricky ApproachPart of the cistern filled in 1 minute by both the taps= $1/40 - 1/60 = {3 - 2}/120 = 1/120$Empty cistern will be filled in 120 minutes.

Question 376. A tap takes 36 hours extra to fill a tank due to a leakage equivalent to half of its inflow. The inflow can fill the tank in how many hours ?

18 hrs
30 hrs
36 hrs
24 hrs

Discuss Question

Answer: Option A. -> 18 hrs
Answer: (a)Using Rule 7,Let the inflow fill the tank in x hours.$1/x - 1/{2x} = 1/36$[leakage being half of inflow]= ${2 - 1}/{2x} = 1/36$2x = 36$x = 36/2$ = 18 hours

Question 377. Three taps A, B and C can fill a tank in 12, 15 and 20 hours respectively. If A is open all the time and B and C are open for one hour each alternatively, the tank will be full in :

7$1/2$ hours
7 hours
6 hours
6$1/2$ hours

Discuss Question

Answer: Option B. -> 7 hours
Answer: (b)Using Rule 1,Two taps 'A' and 'B' can fill a tank in 'x' hours and 'y' hours respectively. If both the taps are opened together, then how much time it will take to fill the tank?Required time = $({xy}/{x + y})$ hrs

Question 378. A tank has two pipes. The first pipe can fill it in 4 hours and the second can empty it in 16 hours. If two pipes be opened together at a time, then the tank will be filled in

5$1/3$ hours
6 hours
5$1/2$ hours
10 hours

Discuss Question

Answer: Option A. -> 5$1/3$ hours
Answer: (a)Using Rule 7,Part of tank filled by both the pipes in 1 hour= $1/4 - 1/16 = {4 - 1}/16 = 3/16$Required time = $16/3 = 5{1}/3$ hours

Question 379. Two pipes A and B can fill a cistern in 37$1/2$ minutes and 45 minutes respectively. Both pipes are opened. The cistern will be filled just in half an hour, if the pipe B is turned off after :

9 minutes
5 minutes
15 minutes
10 minutes

Discuss Question

Answer: Option A. -> 9 minutes
Answer: (a)Pipe A fills the tank in $75/2$ minutes.Part of the tank filled by A in 30 minutes= $2/75 × 30 = 4/5$Remaining part= $1- 4/5 = 1/5$Now, 1 part is filled by pipe B in 45 minutes$1/5$ part is filled in= 45 × $1/5$ = 9 minutesHence, the pipe B should be turned off after 9 minutes.

Question 380. A tank has a leak which would empty the completely filled tank in 10 hours. If the tank is full of water and a tap is opened which admits 4 litres of water per minute in the tank, the leak takes 15 hours to empty the tank. How many litres of water does the tank hold ?

7200 L
1200 L
2400 L
4500 L

Discuss Question

Answer: Option A. -> 7200 L
Answer: (a)
Let the capacity of the tank = x litres
According to the question,
Quantity of water emptied by the leak in 1 hour = $x/10$ litres
Qunatity of water filled by the tap in 1 hour = 240 litres
According to the question,
$x/10 - x/15$ = 240
${3x - 2x}/30 = 240$
$x/30$ = 240
$x$ = 240 × 30 = 7200 litres