Aptitude - Problems on Trains - Discussion

Distance =speed *time.
D=72km/h*26,
D=72*5/18*26,
D=4*5*26,
D=20*26,
D=520-250=270m.

Thank you so much for all your explanations.

Why x+250 is taken? Explain.

The formula used is : time taken by the train = (length of train + length of platform)/ speed of the train.

Where the length of the train is taken as X.

I'll explain you @Sakshi that why we are adding with the distance travelled.

Suppose the train passes through a pole or a stationary man we consider only length of the train as a distance travelled because length of man or pole is negligible but when we come across the platform well have to consider the length of platform also as a distance travelled because the train passes the platform in the given time so lengthy of platform is also added with the length of train.

I still didn't understand why we are adding the length of the train with the distance travelled?

Please anyone explain it.

Shortcut:

Speed of the train is 20 m/sec.

Therefore for 1 sec--20 m.

For 26 sec -- ?

20*26=520/1.

It means for 26 sec train crosses 520m. It includes length of train also, therefore we need minus the length of the train to get the length of the platform.

i.e., 520-250 = 270.

What is SP and TI?

= 72*5/18.
= 36*5/9.
= 4*5.
= 20.

d = Sp*ti.
20*26.
= 520-250.
= 270.

Train speed m/s = 72x5/18 = 20 sec/m.

Length of train = speed x time.

= 26*20 = 520m - 250(length of the platform).

So train length = 270m.

Is it right or wrong?