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 3 of 7.
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.
Robot said:
9 years ago
If you assume the value corresponding to the second pipe to be x,
The other two factors would be x + 5, x - 4 with respect to the 1st and the 3rd pipe.
Here,
1/ (x) + 1/ (x + 5) = 1/ (x - 4).
In this case, the answer turns out to be 10.
Help me.
The other two factors would be x + 5, x - 4 with respect to the 1st and the 3rd pipe.
Here,
1/ (x) + 1/ (x + 5) = 1/ (x - 4).
In this case, the answer turns out to be 10.
Help me.
DEVINDER SINGH said:
2 years ago
Why equating work of a+b = work of c.
till the time we used the method
a = x-5
b = x
c =x-4.
Acc to the question.
(x-5) + x = x-4 on solving;
a = 4.
b = 9.
c = 13 which seems feasible acc conditions and also we used earlier questions.
till the time we used the method
a = x-5
b = x
c =x-4.
Acc to the question.
(x-5) + x = x-4 on solving;
a = 4.
b = 9.
c = 13 which seems feasible acc conditions and also we used earlier questions.
(10)
Chinna jgc said:
1 decade ago
2nd pipe is 5 hours faster than 1st.so 2nd pipe=5x
1st pipe automatically takes 1 hour to fill the tank.1st pipe=1x.
in question 2nd pipe is 4 hours slower than 3rd pipe.
i.e 5x+4x=9x
3rd pipe =9x
add all 3 pipes i.e 1x+5x+9x=15.
1st pipe automatically takes 1 hour to fill the tank.1st pipe=1x.
in question 2nd pipe is 4 hours slower than 3rd pipe.
i.e 5x+4x=9x
3rd pipe =9x
add all 3 pipes i.e 1x+5x+9x=15.
Praneeth said:
1 decade 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.
Lavanya said:
8 years ago
Two pipes M and N can fill a cistern in 24 min and 32 min, repectively. If both the pipes are opened together, then after hoe many minutes N should be closed so that the tank is full in 18 minutes?
Please answer it.
Please answer it.
(1)
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.
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.
Chandni said:
1 decade ago
I solved it by taking 2nd pipe's speed as x.
Then 1st pipe speed would be x-5 and 3rd pipe = x+4.
If we resolve now, we get y = -10 and y = 2.
So, I was finding answer according to 2.
Then 1st pipe speed would be x-5 and 3rd pipe = x+4.
If we resolve now, we get y = -10 and y = 2.
So, I was finding answer according to 2.
(1)
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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