Aptitude - Problems on Trains - Discussion

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

I have solved this problem in a different way, is this the right way to solve it?

Speed=15 m/sec.
Total length of train is 300m,
let length of the plateform be x m,
total distance = speed * time,
x + 300 = 15*36,
x + 300 = 540,
x = 240m.

Answer 240m is possible only if the man is standing at the end of the station.

Am I right or wrong? Please anyone clarify.

Why didn't we added the length of the man? Please explain.

As we know Distance = Speed x Time.

Let's find the length of the train --> to find the distance of a train we have to multiply the speed of the train by the time taken by the train to cross a man or pole. so it comes like 15 x 20 = 300 meters.

So, the length of the train is 300 meters

Now when we multiply the train speed with the time taken to cross the platform..... we get the whole length of the train and also the platform length. LIKE --> 15 x 36 = 540 meters .

Now, this length is the whole length of the platform and the train.

To find the platform length subtract the train length that we found out with the whole length
300 - 540 = 240.

240 is the length of the platform.

Speed = 15mtr/hr.
15*20 = 15 * 36,
300 = 540.
= 540 - 300.
Length = 240.

@All.

Since the train is moving toward the man you can do 36-20 seconds = 16 seconds.

Speed = l + b (length of train +platforn).
Speed of train = 54*5/18 = 15.
speed = d/t -----> d = s*t.
d = 15*36-20 (time of train - time of man).
d = 240m.

The length of platform = x + 300/36 = 15 m/s.

Can someone explain why we write the 15 m/s on R.H.S of the equation?

I really could not understand. If someone knows then please help me.

54 * 5/18 = 15m/sec.
20 + 36sec = 56sec,
15 * 56 = 240m.