Aptitude - Pipes and Cistern - Discussion

Please somebody tell me in easier way.

Looking at the question, it is quite evident that the first two pipes simultaneously fills the tank in same time.

Assuming the time taken by pipe A to fill the tank is X hours, then for every hour, it will fill 1/X of the tank.

Now, "second pipe fills the tank 5 hours faster than the first pipe and 4 hours slower than the third pipe" --> So the second pipe will require lesser time than pipe A to fill tank i.e. (X-5) hours.

Second tank is also 4 hours slower than the third pipe, so third pipe will be X-5-4 = X-9 hours.

Summing up, the equation goes like:

1/X + 1/X-5 = 1/X-9.

Just remember these:

1. Faster fil = lesser time.

2. If total time=x, then for 1 hr it is 1/x.

3. When you get two different answers after solving the equation just substitute the answers (like x=15) in the original equation and check whether it is feasible.

Dear Friends. The solution according to me is correct.

The reason as to why X = 3 is neglected is because there is no negative time.

For example: 3 hrs. If you substitute X with 3, then,

1/(x-5) will be 1/(3-5).

Which are 1/-2 hours (negative thirty minutes: never in real life!)

@Sameeera.

Your solution seems to be apt to this problem. Thank you.

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.

Why you neglect 3?

Is there any shortcut method for solving it?

Why do you neglect 3? What is the reason?

@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.