Question

A train passes a lamp post in7seconds if the length of the train is210m, find the speed of the train

Answer 1

speed of the train 

=390 metre21 sec=1307m/s390 metre21 sec=1307m/s

We know that, 

When train crosses only object that has no distance (i.e. tree lamp post, man etc.) in that condition train covers equal distances to itself. 

So the length of the train 

=1307m/s×7sec1307m/s×7sec

= 130 metres