Pipes & Cistern
Important Instructions
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 in just half an hour, if the B is turned off after:
Answer: B
Let B be turned off after x minutes. Then,
Part filled by (A + B) in x min. + Part filled by A in (30 -x) min. = 1.
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Two pipes M and N are opened together to fill a tank. Both the pipes fill the tank in time X minutes. When M alone is filling the tank, it takes 9 minutes more time than X to fill the tank. In a similar manner N takes 16 minutes more time than X to fill the tank. What is the value of X?
Answer: A
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Two pipes A and B can fill a tank in 24 minutes and 32 minutes respectively. If both the pipes are opened simultaneously, after how much time should B be closed so that the tank is full in 18 minutes?
Answer: C
No explanation is available for this question!
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Pipe P can fill a tank in 38 hours. Pipe Q alone can fill it in 19 hours. Pipe R can empty the full tank in 133 hours. If all the pipes are opened together, how much time will be needed to make the tank full?
Answer: D
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A tank can be filled by a tap in 20 minutes and by another tap in 60 minutes. Both the taps are kept open for 10 minutes and then the first tap is shut off. After this, the tank will be completely filled in what time ?
Answer: C
How we can solve this question ? First we will calculate the work done for 10 mins, then we will get the remaining work, then we will find answer with one tap work, As Part filled by Tap A in 1 min = 1/20 Part filled by Tap B in 1 min = 1/60 (A+B)'s 10 mins work =
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Two pipes M and N can fill a pool in 40 minutes and 60 minutes, respectively. The entire pool can completely be emptied by another pipe P in 30 minutes. M, N and P are opened alternatively and each is kept open for just 1 minute. In how much time will the pool be filled?
Answer: B
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A cistern can be filled in 9 hours but due to a leak at its bottom it takes 10 hours. If the cistern is full, then the time that the leak will take to make it empty will be ?
Answer: C
Part filled without leak in 1 hour = 1/9
Part filled with leak in 1 hour = 1/10
Work done by leak in 1 hour
=1/9-1/10=190
We used subtraction as it is getting empty.
So total time to empty the cistern is 90 hours
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Which of the following fraction is greater than 2/3 and less than 4/5 ?
Answer: C
1/2 = 0.5, 2/3 = 0.66, 4/5 = 0.8, 9/10 = 0.9, 3/4 = 0.75, 5/6 = 0.833,
Clearly, 0.8 lies between 0.75 and 0.833
3/4 lies between 2/3 and 4/5
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If a fraction’s denominator is decreased by 80% and numerator is increased by 300%, the fraction becomes 2/9. What is the fraction?
Answer: C
Let fraction be a/b
80?crease means denominator 20% of original value 0.2b
300% increase means numerator a+300% of a = a+ 3a 4a
Also, new fraction = 4a/0.2b = 2/9
a/b = 1/90
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Two pipes A and B can fill a tank in 20 and 30 minutes respectively. If both the pipes are used together, then how long it will take to fill the tank?
Answer: B
In this type of questions we first get the filling in 1 minute for both pipes then we will add them to get the result, as
Part filled by A in 1 min = 1/20
Part filled by B in 1 min = 1/30
Part filled by (A+B) in 1 min = 1/20 + 1/30
= 1/12
So both pipes can fill the tank in 12 mins.
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