Aptitude - Problems on Trains - Discussion

There is no length for man hence,
L/15 = 20.
L= 300.

And platform has length hence,
L+B/15 =36.
300+B = 540.
B=240.

The second method is, Convert the speed in m/sec.

And man is standing in platform then the both given time is subtract to each other and the subtract answer is multiplied the speed.

D = TxS.
As we mentioned here,
54kmph = 54x(5÷18) = 15mps.

D = TxS.
= (36-20)x15.
= 16x15.
= 240mts.

Why we cannot take 15*36.

Because dist = speed x time know. 36seconds is also speed only know.

(36-20)X(54X(5/18)) = 240.

Here is the logic of why we need the train length.

Because trains enter the platform from the engine side and leave the platform from the tail side.

So it will consume more time as of the train length, therefore, we need to calculate the length of the train and subtract it from the total length we get which is 36*15 = 540 which is logical so after subtracting train length from it 540-300 = 240.

So now train when leaves the platform we subtract 300 (length of train) so it leaves the platform 300m early which engine point.

Hope this is not confusing.

Length of the train relative to the station is 36*15=540,
Length of the train relative to man@20sec is
20*15=300.

Now,
Length of the train relative to station subtract the length of man 540-300=240.

The train passes a station 36.
Man on platform 20.
Loss of time man 36-20=16.

Speed = distance/time.
15m/sec = L/16.
15x16 = 240 m.

Just subtract the time taken by train to pass a man with the time taken by a train to pass a station i.e 36-20 = 16.

16*15(speed in meters) = 240 meters.

Why we have to multiple 15*20?