Aptitude - Pipes and Cistern - Discussion
Discussion Forum : Pipes and Cistern - General Questions (Q.No. 5)
5.
A tank is filled by three pipes with uniform flow. The first two pipes operating simultaneously fill the tank in the same time during which the tank is filled by the third pipe alone. The second pipe fills the tank 5 hours faster than the first pipe and 4 hours slower than the third pipe. The time required by the first pipe is:
Answer: Option
Explanation:
Suppose, first pipe alone takes x hours to fill the tank .
Then, second and third pipes will take (x -5) and (x - 9) hours respectively to fill the tank.
 |
1 | + | 1 | = | 1 |
| x | (x - 5) | (x - 9) |
 |
x - 5 + x | = | 1 |
| x(x - 5) | (x - 9) |
(2x - 5)(x - 9) = x(x - 5)
x2 - 18x + 45 = 0
(x - 15)(x - 3) = 0
x = 15. [neglecting x = 3]
Discussion:
68 comments Page 5 of 7.
Manasa said:
1 decade ago
@pranesh kumar
In options "3" is not given...so we considered 15
both "3" and "15" are correct.
@karthikeyan
In the question they given
The first two pipes operating simultaneously fill the tank(1/x+1/X-5)... in the same time means ("=") during which the tank is filled by the third pipe alone(1/X-9)
how much water gets filled up by the first two pipes in 1 hour...the same amount of water gets filled up by the third pipe in 1 hour.
In options "3" is not given...so we considered 15
both "3" and "15" are correct.
@karthikeyan
In the question they given
The first two pipes operating simultaneously fill the tank(1/x+1/X-5)... in the same time means ("=") during which the tank is filled by the third pipe alone(1/X-9)
how much water gets filled up by the first two pipes in 1 hour...the same amount of water gets filled up by the third pipe in 1 hour.
Prasad said:
1 decade ago
How you have taken 9 hours?
Vaisakh said:
10 years ago
Let first pipe alone takes x hours to fill the tank. Then if we take (x+5), it means 2nd pipe fills the tank 5 hours slower than the first pipe. So it's not possible. Just think about it.
Rohit sharma said:
1 decade ago
Is it wrong if we suppose X time taken by the 2nd pipe and solve as per the problem i.e :
Time taken by 1st pipe : X+5.
Time taken by 2nd pipe : X.
And time taken by 3rd pipe : X-4.
Please explain me.
Time taken by 1st pipe : X+5.
Time taken by 2nd pipe : X.
And time taken by 3rd pipe : X-4.
Please explain me.
Tanu said:
1 decade ago
1st can fill tank in x hrs.
2nd can fill 5 hrs faster than 1st = x - 5.
3rd is 4 hr faster than 1st = (x - 5) -4 = x-9.
Hence,
1/x +1/(x-5) = 1/(x - 9).
2nd can fill 5 hrs faster than 1st = x - 5.
3rd is 4 hr faster than 1st = (x - 5) -4 = x-9.
Hence,
1/x +1/(x-5) = 1/(x - 9).
SABYASACHI said:
1 decade ago
Is there any short tricks for this type of questions?
SABYASACHI said:
1 decade ago
How it became (x-5) and (x-9) ?
Thekingoftheworld said:
1 decade ago
The resolution here presented lies on the assumption that the volume is 1 cubic meter.
In fact, this problem would have infinite solution as no volume is specified in the question.
In fact, this problem would have infinite solution as no volume is specified in the question.
Pulkit said:
1 decade ago
Can anybody answer my question with correct explanation that why we have neglected x=3 and answered x=5. I know the explanation but I want to now that does anybody else knows it.
Inu said:
1 decade ago
Time cannot be negative. Thats why 3 is neglected.
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