A train crosses a 900 metres long platform in 300 seconds. If the length of train is 600 metres. then in how much time does it cross a stationary pole?

Speed = $$ \frac{Distance}{Time} $$

train crosses a 900 metres long platform in 300 seconds.

 length of train is 600 metres.

Total distance = length of the train + length of the platform

                      = 900 + 600 = 1500

Speed = $$ \frac{1500}{300} = 5 m/s $$

To cross a stationary pole Time = $$ \frac{Distance}{Speed} $$

substituting,

Time = $$ \frac{600}{5} = 120 s $$

120 seconds = $$ \frac{120}{60}$$ = 2 minutes