Aptitude - Pipes and Cistern - Discussion
Discussion Forum : Pipes and Cistern - General Questions (Q.No. 4)
4.
Two pipes A and B can fill a cistern in 37
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:
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: Option
Explanation:
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.
 x |
 |
2 | + | 1 |  |
+ (30 - x). | 2 | = 1 |
| 75 | 45 | 75 |
 |
11x | + | (60 -2x) | = 1 |
| 225 | 75 |
11x + 180 - 6x = 225.
x = 9.
Discussion:
91 comments Page 5 of 10.
Kunal Aryan said:
9 years ago
For this type of question use Short Trick :
[Y*(1 - t / x)]
Here X= 75/2 ; Y=45 and t= 30mint. (ie. half an hour).
Soln: 45*(1 - 30 * 2 / 75) = 9 mints. answer.
[Y*(1 - t / x)]
Here X= 75/2 ; Y=45 and t= 30mint. (ie. half an hour).
Soln: 45*(1 - 30 * 2 / 75) = 9 mints. answer.
Hemant said:
9 years ago
In 1min=2/75 part of the cistern is filled by pipe A.
And In 1 min=1/45 part of the cistern is filled by pipe B.
Now,
Pipe A worked for 30 min and pipe B work for x min we suppose,
To fill complete cistern = 1 part.
2/75 * 30 + 1/45 * x = 1,
12/15 + x/45 = 1,
(36 + x)/45 = 1,
x = 9 min.
And In 1 min=1/45 part of the cistern is filled by pipe B.
Now,
Pipe A worked for 30 min and pipe B work for x min we suppose,
To fill complete cistern = 1 part.
2/75 * 30 + 1/45 * x = 1,
12/15 + x/45 = 1,
(36 + x)/45 = 1,
x = 9 min.
Satendra singh said:
9 years ago
(30-X) how came? Please explain me.
Sudhakar p said:
9 years ago
I can't understand please explain clearly.
Naidu said:
9 years ago
How 30 came after 2/75?
Ranjit said:
9 years ago
@Arshad 1605.
How the answer 9 came after the step 105/11?
How the answer 9 came after the step 105/11?
Kumar said:
9 years ago
@Arshad1605, Please tell me how 9 came after 105/11?
Kouser said:
9 years ago
Good explanation @Kasi Srinivas.
Aka said:
9 years ago
Yet simpler approach:
A's 1 minute work = 2/75,
B's 1 minute work = 1/45,
Let B be opened for first x minutes while A is opened for entire 30 mins.
=> 2/75 * 30 + 1/45 * x = 1.
By solving it, we get the answer.
A's 1 minute work = 2/75,
B's 1 minute work = 1/45,
Let B be opened for first x minutes while A is opened for entire 30 mins.
=> 2/75 * 30 + 1/45 * x = 1.
By solving it, we get the answer.
(1)
Ashok said:
9 years ago
Go from the option.
Choose option 9 minutes and use it in B 1 minute work = 1/45 and find it for 9 minutes it's 1/5 then go for remaining works it is 1-1/5 = 4/5. This remaining work will be done by A then.
4/5 work in 75/2 minutes 4/5 * 75/2 = 30 that is the given minutes taken to fill the tank.
Choose option 9 minutes and use it in B 1 minute work = 1/45 and find it for 9 minutes it's 1/5 then go for remaining works it is 1-1/5 = 4/5. This remaining work will be done by A then.
4/5 work in 75/2 minutes 4/5 * 75/2 = 30 that is the given minutes taken to fill the tank.
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