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) 3$1/3$ hours
(b) 7$1/2$ hours
(c) 2$2/5$ hours
(d) 2$1/3$ hours
The correct answers to the above question in:
Answer: (a)
Using Rule 1,
Part of tank filled by pipes A and B in 2 hours
= $2(1/6 + 1/8)$
=$2({4 + 3}/24) = 7/12$
Remaining part = $1 - 7/12 = 5/12$
This part is filled by pipe B.
Required time = $5/12$ × 8
= $10/3$ hours = 3$1/3$ 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 fill a tank in 20 minutes and 30 minutes respectively. If both pipes are opened together, the time taken to fill the tank is :
a) 15 minutes
b) 50 minutes
c) 12 minutes
d) 25 minutes
Answer »Answer: (c)
Part of the tank filled by both pipes in one minute
= $1/20 + 1/30$
Required time = $1/{1/20 + 1/30}$
= ${20 × 30}/50$ = 12 minutes
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
Here, x = 20, y = 30
Required time = $({xy}/{x + y})$ minutes
= $({20 × 30}/{20 + 30})$ minutes = 12 minutes.
Question : 2
One tap can fill a water tank in 40 minutes and another tap can make the filled tank empty in 60 minutes. If both the taps are open, in how many hours will the empty tank be filled ?
a) 3.5 hours
b) 2 hours
c) 2.5 hours
d) 3 hours
Answer »Answer: (b)
Using Rule 7,
Part of the tank filled when both taps are opened together
= $1/40 - 1/60 = {3 - 2}/120 = 1/120$
Hence, the tank will be filled in 120 minutes 2 hours.
Question : 3
Two pipes A and B can fill a cistern in 3 hours and 5 hours respectively. Pipe C can empty in 2 hours. If all the three pipes are open, in how many hours the cistern will be full?
a) 30 hours
b) can’t be filled
c) 10 hours
d) 15 hours
Answer »Answer: (a)
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.
Part of cistern filled by three pipes in an hour
= $1/3 + 1/5 - 1/2 = {10 + 6 - 15}/30 = 1/30$
Hence, the cistern will be filled in 30 hours.
Question : 4
Two pipes A and B can separately fill a tank in 2 hours and 3 hours respectively. If both the pipes are opened simultaneously in the empty tank, then the tank will be filled in
a) 1 hour 20 minutes
b) 1 hour 12 minutes
c) 2 hours 30 minutes
d) 1 hour 15 minutes
Answer »Answer: (b)
Using Rule 1,
Part of tank filled by pipes A and B in 1 hour
= $1/2 + 1/3 = {3 + 2}/6 = 5/6$ parts
Required time = $6/5$ hours
= 1 hour $1/5$ × 60
= 1 hour 12 minutes
Question : 5
Three taps A, B, C can fill an overhead tank in 4, 6 and 12 hours respectively. How long would the three taps take to fill the tank if all of them are opened together ?
a) 5 hrs.
b) 2 hrs.
c) 4 hrs.
d) 3 hrs.
Answer »Answer: (b)
Using Rule 2,
Part of the tank filled by all three taps in an hour
= $1/4 + 1/6 + 1/12 = {6 + 4 + 2}/24 = 1 2$
Hence, the tank will be filled in 2 hours.
Question : 6
If two pipes function simultaneously, a tank is filled in 12 hours. One pipe fills the tank 10 hours faster than the other. How many hours does the faster pipe alone take to fill the tank?
a) 12 hrs
b) 20 hrs
c) 18 hrs
d) 15 hrs
Answer »Answer: (b)
Using Rule 1,
If the slower pipe fills the tank in x hours, then
$1/x + 1/{x - 10} = 1/12$
${x -10 + x}/{x(x - 10)} = 1/12$
$x^2 - 10x = 24x - 120$
$x^2 - 34x + 120$ = 0
$x^2 - 30x - 4x + 120$ = 0
$x (x - 30) - 4 (x - 30)$ = 0
$(x - 4) (x - 30)$ = 0
$x$ = 30 because $x ≠ 4$
Required time = 30 - 10 = 20 hours
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
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