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 3 of 10.
Deepak said:
8 years ago
Best solution:
Parts filled by A in 1 min = 2/75
Parts filled by B in 1 min = 1/45
Now;
In 30 min tank is full so,
Parts filled by A in 30 min = 30*2/75 =60/75
Parts filled by B in X min = X/45
So, 60/75 + X/45 = 1
Therefore ,X = 9 min.
Parts filled by A in 1 min = 2/75
Parts filled by B in 1 min = 1/45
Now;
In 30 min tank is full so,
Parts filled by A in 30 min = 30*2/75 =60/75
Parts filled by B in X min = X/45
So, 60/75 + X/45 = 1
Therefore ,X = 9 min.
Leela said:
8 years ago
Thanks @Deepak.
Arjun said:
8 years ago
Nice work @Kasi Srinivas.
Devi said:
6 years ago
For this type of question, we can approach like;
Here pipe A fill-in 75/2min(let it be 'x'), pipe B in 45 min(let it be 'y').
At what time B pipe should be close to fill a total cistern in 30 min (let it be 't'min)is,
y(1-(t/x))= 45(1-((30*2)/75)) = 9min.
Here pipe A fill-in 75/2min(let it be 'x'), pipe B in 45 min(let it be 'y').
At what time B pipe should be close to fill a total cistern in 30 min (let it be 't'min)is,
y(1-(t/x))= 45(1-((30*2)/75)) = 9min.
Manikant said:
8 years ago
2/75 + 1/45 = 8/225.
How it can be 11/225?
How it can be 11/225?
Sandhiya said:
8 years ago
Can anyone explain how 2/75 comes? please.
Madhubala said:
8 years ago
For 1min it takes( 2/75).
For 30 min (1/2 hour) it takes 2/75*30=4/5 part.
So remaining only 1 part out of 5 which is going to fill by B.
So (1/5*45) = 9 min.
For 30 min (1/2 hour) it takes 2/75*30=4/5 part.
So remaining only 1 part out of 5 which is going to fill by B.
So (1/5*45) = 9 min.
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.
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers