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 3 of 7.
Pranesh kumar said:
2 decades ago
Why you neglect x=3 for what reasons?
(1)
Sachin said:
1 decade ago
How can a pipe fill in both 3 and 9 hours. Hows it possible?
Only one answer must be true?
which one how to get?
Only one answer must be true?
which one how to get?
(1)
Karthikeyan said:
2 decades ago
How got this equation 1/x+1/x-5=1/x-9 ?
(1)
Swapnil said:
8 years ago
1/x + 1/ (x-5) = 1/(x-9).
Why 1/(x-9) equate with 1/x + 1/ (x-5)?
Why 1/(x-9) equate with 1/x + 1/ (x-5)?
(1)
Monu dhaka said:
9 years ago
@Lavanya.
Answer is 10 minutes {(18/24)+(8/32)}=1.
18-8 = 10minutes.
Answer is 10 minutes {(18/24)+(8/32)}=1.
18-8 = 10minutes.
Virajgouda said:
10 years ago
Why do you neglect 3? What is the reason?
Prawesh Pradhan said:
10 years ago
@Virajgouda, if take X as 3 the answer will be negative. And time can't be negative. X - 5 and x - 9 would be -2 and -6.
Bhagyasree said:
9 years ago
Suppose A takes x hours then B takes x-5 hours.
Ex: It means that A completed in 10 hours where B Completed only in 5 hours
Now C take y hours where B Completes in y+4 hours(slower),
So x-5 =y+4..............y=x-9,
Here capability of A+B = C,
1/x+1/x-5 = 1/y,
Now, You can easily solve this eq 1/x+1/x-5 = 1/x-9.
Ex: It means that A completed in 10 hours where B Completed only in 5 hours
Now C take y hours where B Completes in y+4 hours(slower),
So x-5 =y+4..............y=x-9,
Here capability of A+B = C,
1/x+1/x-5 = 1/y,
Now, You can easily solve this eq 1/x+1/x-5 = 1/x-9.
Reshma said:
9 years ago
Nice explanation @Tanu.
Prasad said:
2 decades ago
How you have taken 9 hours?
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