To determine the velocity of the man relative to the boy standing by the road, we need to calculate the relative velocity by considering the velocities of both the man and the train.
Let's assume that the train is moving to the right, and the man is walking in the opposite direction, to the left.
The velocity of the train is given as 20 km/h (to the right). The velocity of the man walking is given as 5 km/h (to the left).
To find the relative velocity of the man with respect to the boy standing by the road, we need to subtract the velocity of the train from the velocity of the man:
Relative velocity = Velocity of the man - Velocity of the train
Since the man is walking in the opposite direction, we take the negative sign for his velocity:
Relative velocity = (-5 km/h) - (20 km/h) = -25 km/h
The negative sign indicates that the man is moving in the opposite direction to the train and the boy standing by the road.
Therefore, the velocity of the man relative to the boy standing by the road is 25 km/h in the opposite direction of the train.