Aptitude - Problems on Trains - Discussion

Length = Speed * Time.
Speed = 54 * 5/18 = 15 m/sec.
Time = 36 - 20 = 16.
Length = 15 * 16.
= 240m.

There are a platform and train is passing through that platform in 36 seconds and there is a man ON THE PLATFORM, the train passes it in 20 sec. You cannot add both the times because man is standing on the platform. If he were standing outside the platform timings could have been added.

So, Trains speed is 15 m/s and it is a crossing platform in 36 seconds and men is included in it coz he is standing on the platform.
So length of train + length of platform will be = 15 multiply 36 = 540.

Now the length of the platform (you have to subtract the length of the train from total length) = 15 multiply 20 = 300.
So, 540 - 300 = 240.

SIMPLE WAY.

Speed = 54km/hr,
54/3600 * 1000,
=15m/s.

36 sec to pass the platform
15 * 36 = 540.
20 sec to pass the man,
15 * 20 = 300.
i.e distance is 540 - 300 = 240.

Speed of the train = 54km/hr,
= 54 * 5/18 m/s,
= 15 m/s.

Time = train reach time - man standing time.
= 36 - 20,
= 16s.

Length = Speed * time.
= 15 * 16.
= 240m.

Distance = time * speed.

Sspeed of train = 54 * 5/18 = 15 m/s.
Time taken by train to cross man= 20s,
Therefore distance/length of train = 20 * 15 = 300m,
Time taken to cross platform= 36s.
Length of train + length of platform = time * speed.
Which implies,
Length of platform = (36 * 15) - length of train.
Length of platform = 540 - 300,
Length of platform = 240m.

54 * (5/18) = 15m.
x = 36s y = 20s.
x - y = 16s (dist b/w train reach the station - train reach the man).

Now,
15 * 16 = 240m (speed * dist).
Answer = 240m.

I am unable to understand it. Someone help me.

I think there should be clarified in the question. That the man is exactly standing the place as the train is long.

Then only we can take the train length according to given solution.

Otherwise, the solution is wrong.

According to my understanding,

1- In 36s train passes the total length which is unknown.
2- In 20s train passes the man which will be our reference point to calculate the speed.

So, from formula: Length or Distance = Time * Speed.

Length of train = 20s * 54(1000/60 * 60).
Length of train = 300 m.

Total length (Platform & train) = 36s * 54(1000/60 * 60).
Total length (Platform & train) = 540m.

Platform length = Total length = Train length = 540 -300 = 240m.

The length of the train = the time * speed
= 15 * 20 seconds taken by it to pass the man as the man is standing at one point.
= 300m

The length of the platform = remaining time * speed.
= (36 - 20) * 15.
= 16 * 15.
= 240.