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:
90 comments Page 5 of 9.
Azharudhin said:
9 years ago
Hi @Meraj Husain, please explain how 60 came?
Your explanation is nice, please explain clearly once again. Thank you for your comments.
Your explanation is nice, please explain clearly once again. Thank you for your comments.
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.
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)
Kouser said:
9 years ago
Good explanation @Kasi Srinivas.
Kumar said:
9 years ago
@Arshad1605, Please tell me how 9 came after 105/11?
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?
Naidu said:
9 years ago
How 30 came after 2/75?
Sudhakar p said:
9 years ago
I can't understand please explain clearly.
Satendra singh said:
9 years ago
(30-X) how came? Please explain me.
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.
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