Aptitude - Pipes and Cistern - Discussion

Above ans is right. Thing this way.....we want to find the time that the slower pipe alone can fill the tank not the time from total 36mins hence we take 1/A+1/b=1/36 so that we are finding the time from 100% and not from 36 mins. We are basically generalizing by taking the numerator as 1.

Why do we need to take time as 1/time?

Whenever we say ram works twice as fast as shyam in a given timeframe. it means it takes two shyams to complete that work in that given timeframe because single shyam can only do half of ram's capacity. kindly always keep this common sense in mind while attempting these kind of ques independent of their form.

So solution: one pipe works 3 times faster than other..let name of this pipe A
let name of other pipe (slower)B

B is equivalent to shyam here..so if both pipes can fill one tank in 36 mins. both means A+B and as per our common sense A is equivalent to 3 B's. therefore
(B+B+B)+B = 36
B = 36/4? NOT POSSIBLE
as if 4 people can do a work in 1 min then 1 person will do it in 4*1 mins. coz more people less time and less people more time.

What we understand by this is timse is inversely proportional to work done. therefore if four B's doing it in 36 mins then single B will do it in 4*36 = 144.

Great kailash.

Kailash you are genious.

If i take A =x and B=3x then I am getting 27 min as answer is it wrong?

If I assume x as time then A = 9 and B =27 after calculating x+3x=36 is it wrong? please explain.

The simplest way is.

Together the two pipes can fill in 36 min.

That means the fastest one can fill 36*3=108.

And the slowest one is =108+36=144.

We may also solve in this manner i.e.

x + x/3 =36
=>
4x/3 = 36
or =>

x=27

@Laxman:.

Your way of approaching to the problem is good, simple and understandable.

Slower pipe x,faster 3x....
1/x+1/3x=1/36
=>x=48

then 1/36-1/48
we got 1/144