A train passes two persons walking in the same direction at a speed of 3 km/hr and 5 km/hr respectively in 10 seconds and 11 seconds respectively. The speed of the train is :

Solution(By Examveda Team)

Let the train's speed = x km/hr
  $$\because \,$$ When train will cross a man then it covers only its length.
$$\eqalign{ & \therefore \left( {x - 3} \right) \times \frac{{10}}{{60}} = \left( {x - 5} \right) \times \frac{{11}}{{60}} \cr & x = 25{\text{ km/hr}} \cr} $$
Note :
Products of time × speed is always subtracted if both the men are running in the same direction and the products of time × speed is added only if the men are running opposite direction.
⇒ Here train's direction is not considered.
But attention please ⇒ Always divided by the difference of time.