Aptitude - Problems on Trains - Discussion

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.

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

Why we cannot take 15*36.

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

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

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

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.

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.

54*5/18 = 15m/sec.
36-20 = 16 seconds.
Distance = speed *time.
Distance = 15m/sec*16 seconds.
Distance = 240m.

According to speed of trai = 15m/s.
And time = 36-20 = 16sec.
Therefore length of platform = 15x16 = 240m.

Any one please explain me.

Simply;

Find speed in m/sec
54*(5/18).

And the difference between two lengths from plat1 to plat2 i,e (36-20)=16 and this is to the time taken to cross length plat1 to plat2 in secs.

As we know s=d/t;
5/18*16=240; answer