A train 125 m long passes a man, running at 5 km/hr in the same direction in which the train is going, in 10 seconds. The speed of the train is:

Given Data

• Train length = 125 m
• Man's speed = 5 km/hr
• Overtaking time = 10 s
• Direction = same (use relative speed = v_train − v_man)

Step 1: Compute relative speed from distance and time Relative distance to overtake = train length = 125 m Time = 10 s Relative speed (m/s) = Distance ÷ Time = 125 ÷ 10 = 12.5 m/s

Step 2: Convert relative speed to km/hr 1 m/s = 3.6 km/hr Relative speed = 12.5 × 3.6 = 45 km/hr

Step 3: Get train's actual speed (same direction) v_train − v_man = 45 v_train = 45 + 5 = 50 km/hr

Sanity Check (all in m/s) v_man = 5 × (5/18) = 1.388... m/s v_train = 12.5 + 1.388... = 13.888... m/s = 13.888... × 3.6 = 50 km/hr ✔

Final Answer The speed of the train is 50 km/hr.