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 6 of 7.
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.
Debasish said:
10 years ago
Is there any shortcut method for solving it?
Inu said:
1 decade ago
Time cannot be negative. Thats why 3 is neglected.
Sameeera said:
1 decade ago
Why can't we solve it in this way:
Let c=3rd pipe, b=2nd pipe, a=1st pipe.
Let us fix c's time = x.
c=x ; a=x+9; b=x+4.
(a+b)'s time =c's time.
1/(x+9) + 1/(x+4) = 1/x.
By solving we get x=6.
Now a=9+6=15.
Ok I think you have understood.
Let c=3rd pipe, b=2nd pipe, a=1st pipe.
Let us fix c's time = x.
c=x ; a=x+9; b=x+4.
(a+b)'s time =c's time.
1/(x+9) + 1/(x+4) = 1/x.
By solving we get x=6.
Now a=9+6=15.
Ok I think you have understood.
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.
Deepak Pareek said:
1 decade ago
Solve through options. It will be easier.
Lakshmichandra said:
1 decade ago
Here why we can not consider x+5? I did not understand this problem can any please explain?
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