a train running at the speed of 180 km hr crosses a 365 meter long platform in 21sec. what is the length of the train

Answer 1

180 km/hr = 50 m/s

the front of the train arrives at t=0.

The front of the train leaves the platform at t = 365/50 = 7.3

The back of the train whose length is x leaves the platform at t = 7.3 + x/50

So, solve for x in

7.3 + x/50 = 21