Aptitude - Problems on Trains - Discussion

@ALL.

Logically, the length of the train should be more or less equal to the length of the platform else it will be troublesome for the passengers to cover that distance. And the solution assumes that the man is standing at the beginning of the platform.

Why we multiply 15*20?

36 - 20 = 16,
54 * 5/18 = 15,
16 * 15 = 240.

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.

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.

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.

I am unable to understand it. Someone help me.

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.

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.

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.