Model 1 Basic Pipes & Cisterns problems Section-Wise Topic Notes With Detailed Explanation And Example Questions
MOST IMPORTANT quantitative aptitude - 3 EXERCISES
The following question based on pipes & cisterns topic of quantitative aptitude
(a) ${xy}/{x - y}$ hours
(b) ${xy}/{y - x}$ hours
(c) x - y hours
(d) y - x hours
The correct answers to the above question in:
Answer: (b)
When both pipes are opened simultaneously,
part of the tank filled in 1 hour
= $1/x - 1/y = {y - x}/{xy}$
Required time = ${xy}/{y - x}$ hours
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Read more basic pipes and cisterns problems Based Quantitative Aptitude Questions and Answers
Question : 1
Two pipes A and B can separately fill a cistern in 60 minutes and 75 minutes respectively. There is a third pipe in the bottom of the cistern to empty it. If all the three pipes are simultaneously opened, then the cistern is full in 50 minutes. In how much time the third pipe alone can empty the cistern?
a) 90 minutes
b) 110 minutes
c) 100 minutes
d) 120 minutes
Answer »Answer: (c)
Using Rule 2,If x, y, z, ........... all taps are opened together then, the time required to fill/empty the tank will be:$1/x ± 1/y ± 1/z ± ... = 1/T$Where T, is the required timeNote: Positive result shows that the tank is filling and Negative result shows that the tank is getting empty.
Let the third pipe empty the cistern in x minutes.
Part of cistern filled in 1 minute when all three pipes are opened simultaneously
= $1/60 + 1/75 - 1/x$
According to the question,
$1/60 + 1/75 - 1/x =1/50$
$1/x = 1/60 + 1/75 - 1/50$
= ${5 + 4 - 6}/300 = 3/300 ⇒ 1/x = 3/300$
$x = 300/3$ = 100 minutes
Question : 2
Two pipes can fill a cistern separately in 10 hours and 15 hours. They can together fill the cistern in
a) 9 hours
b) 6 hours
c) 7 hours
d) 8 hours
Answer »Answer: (b)
Using Rule 1,
Part of the cistern filled by both pipes in 1 hour
= $1/10 + 1/15 = {3 + 2}/30 = 1/6$
The cistern will be filled in 6 hours.
Question : 3
A cistern is provided with two pipes A and B. A can fill it in 20 minutes and B can empty it in 30 minutes. If A and B be kept open alternately for one minute each, how soon will the cistern be filled ?
a) 120 minutes
b) 121 minutes
c) 110 minutes
d) 115 minutes
Answer »Answer: (d)
Using Rule 7,
Part of the tank filled in first two minutes
= $1/20 - 1/30 = {3 - 2}/60 = 1/60$
Part of tank filled in 114 minutes
= $57/60 = 19/20$
Remaining part of cistern will be filled in 115th minute
GET pipes & cisterns PRACTICE TEST EXERCISES
Model 1 Basic Pipes & Cisterns problems
Model 2 Filling tank by parts or fractions
Model 3 Opening both taps and leaks
pipes & cisterns Shortcuts and Techniques with Examples
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