Aptitude - Problems on Trains - Discussion

As the man is not moving and he can be ignored as a little particle because he has not such a big length (his standing distance) as a pillar.

So if we take the time of the train passes the man, we can get the exactly length of the train.

So there, the length of the train= (15*20).

If the man would have moving, there we can't take the same length.

We are not taking the time of the platform because it has a big length which can't be ignored.

Time taken by train to pass a station platform = 36 seconds.
Time taken by train to pass a man on platform = 20 seconds.
Speed of train = 54 km/hr.
= ( 54 * 5/18,
= 3 * 5,
= 15 m/s.

length of train = 15 *20.
= 300 m.

Let the length of train be x.
Then;
300 + x /36 = 15.
300 + x = 15*36,
x= 540 -300,
x =260.

So, length of the platform is 240m.

Thanks @Satheesh.

In this problem, it is considered that the man is standing at the extreme end. That's the reason length of the train is calculated as 15*20. What if the man is standing in the middle of the platform.

From the given data, we can consider the only man as a reference point to find the length of train. So let us consider man is standing at the beginning, so 15*20 will be enough to find the length of the train, Am I right?

You can multiply 15 * 36 which gives you 540m then x be the length of the platform therefore as speed = distance upon time 540 +x/20 = 15.

x = 240m.

t1-t2 = 36 - 26 = 16.

We know 54 x 5/18=15,
So putting in formula s=d/t.
15 = d/16, where d is taken as length here;
d = 15 * 16,
= 240.

Why we, not multiple 15 * 36 instead we multiple 15 * 20? Please explain.

Why they have taken 20 sec. Can we take 30 sec also? Please explain.