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 2 of 9.
Amitha said:
1 decade ago
Good explanation -K @ $!
S.MEENAKSHI said:
1 decade ago
Excellent explanation KASI.
Sandip said:
1 decade ago
Here " 1 " means the complete part of the cistern....we learnt such theory in early school days.
Rupinder said:
1 decade ago
@Sandip: That's what aptitude is meant for, i.e., How much knowledge we've dragged with us from our primary schooling, which indicated how consistent the candidate was throughout his academic period. Aptitude marks tells this apparently. And that's what recruiter is looking for, a consistency. Plus it tells your mental ability to grasp the things and to sort it out
Neha sharma said:
1 decade ago
@Mahesh Patil.
What's the logic behind the short cut?
What's the logic behind the short cut?
Pintu Francis said:
1 decade ago
Y going complicated? be simple.
A work in 1 min 2/75.
B work in 1 min 1/45.
So,
(2/75) 30+ (1/45) x=1.
Since A work for 30 min and B for x min.
Solving X=9.
A work in 1 min 2/75.
B work in 1 min 1/45.
So,
(2/75) 30+ (1/45) x=1.
Since A work for 30 min and B for x min.
Solving X=9.
Nags said:
1 decade ago
In (2/75)30+(1/45)x = 1.
Where how 30 will come?
I can't understand.
Where how 30 will come?
I can't understand.
MERAJ HUSAIN said:
1 decade ago
I can get you understood here:
Since cistern is one which is to be filled by A & B.
Hence 1 = work of 1 min of A *30+work in 1 min of B*x.
1 = (2/75)*30+(1/45)*x.
x/45 = 1-60/75 = 15/75 = 1/5.
x = (1/5)*45 = 9 mins.
Since cistern is one which is to be filled by A & B.
Hence 1 = work of 1 min of A *30+work in 1 min of B*x.
1 = (2/75)*30+(1/45)*x.
x/45 = 1-60/75 = 15/75 = 1/5.
x = (1/5)*45 = 9 mins.
Arshad1605 said:
1 decade ago
In 1 minute, both together will fill 2/75 + 1/45 = 11/225 of the cistern.
Cistern should be thus filled in 225/11 minutes.
But cistern filled in 30 minutes.
Therefore, B turned after 30 - 225/11 = (330 - 225)/11.
= 105/11.
= 9(6/11).
Hence B turned off after 9 minutes.
Cistern should be thus filled in 225/11 minutes.
But cistern filled in 30 minutes.
Therefore, B turned after 30 - 225/11 = (330 - 225)/11.
= 105/11.
= 9(6/11).
Hence B turned off after 9 minutes.
Saurav said:
1 decade ago
Why x*(A+B)+A*(30-x) = 1.
It should be x*(A+B)+A*(30-x) = 1/2, because after 30 mins the tank should be half filled?
It should be x*(A+B)+A*(30-x) = 1/2, because after 30 mins the tank should be half filled?
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