Question

a 200 m long train crosses a platform of double its length in 36 s the speed of train is

Answer 1

Initially consider the head of the train to be just adjacent to the edge of the station and when it crosses the station consider its tail to be adjacent to the edge of the station. The head is $200m$ front of the tail. So,$\text{Total distance covered by the head of the train}=\text{Length of platform}+\text{Length of train}\\=400+200=600m\\v=\frac{d}{t}=\frac{600}{36}=16.67\frac{m}{s}$