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:
69 comments Page 5 of 7.
Kasi Srinivas said:
1 decade ago
@ sai :
first pipe alone takes x hours to fill the tank => in 1 hour 1/x part of the work is completed.
similar way we get 1/(x-5) and 1/(x-9) part of the work is completed in 1 hour.
it is the standard practice that we consider the work done in an hour.
If you understood the question properly, you can understand this :)
first pipe alone takes x hours to fill the tank => in 1 hour 1/x part of the work is completed.
similar way we get 1/(x-5) and 1/(x-9) part of the work is completed in 1 hour.
it is the standard practice that we consider the work done in an hour.
If you understood the question properly, you can understand this :)
Sai said:
1 decade ago
Why we have taken 1/x, 1/x-5, 1/x-9. Please can any one say me the reason?
Praneeth said:
2 decades ago
We have considered the x-5 and x-9 as time taken by 2nd and 3rd pipes, but after substituting x=3 we will get -2hr and -7hr respectively for the 2nd and third pipes.
So, we cant have negative values for time practically.
So, we cant have negative values for time practically.
Anonymous said:
5 years ago
Thanks @Sai Krishna.
Manasa said:
2 decades 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:
2 decades ago
How you have taken 9 hours?
Minion said:
1 decade ago
@Sameeera.
Your solution seems to be apt to this problem. Thank you.
Your solution seems to be apt to this problem. Thank you.
Inu said:
1 decade ago
Time cannot be negative. Thats why 3 is neglected.
Lakshmi said:
1 decade ago
Why neglecting 3 in the answer please can any one say?
Vicky said:
1 decade ago
Can you explain that 1/x-9 how come to right hand side positive.
Its positive on left side so it may be come to the right side than the equation -1/x-9.
Please any body explain.
Its positive on left side so it may be come to the right side than the equation -1/x-9.
Please any body explain.
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