Question

A man watches a train crossing 600 m long bridge in 70 seconds. If the speed of the train is 45 km/hr, find the length of the train.

Answer 1

Speed = 45 Km/hr = 45*(5/18) m/sec 
= 25/2 m/sec
Total distance = 360+140 = 500 meter

Time = Distance/speed 
\begin{aligned}
= 500*\frac{2}{25} = 40 seconds
\end{aligned}