A train runs at 40 km/h. A man travels in the same direction on a parallel road at 25 km/h. If the train crosses the man in 48 seconds, what is the length of the train (in meters)?

Introduction / Context:
With same-direction motion, the relative speed is the difference of speeds. The train covers its own length relative to the man in the given time, letting us compute length directly.

Given Data / Assumptions:

• Train speed = 40 km/h.
• Man speed = 25 km/h.
• Overtaking time = 48 s.

Concept / Approach:
Relative speed v_rel = (40 − 25) km/h = 15 km/h = 15 * (1000/3600) = 4.166... m/s. Length L = v_rel * time.

Step-by-Step Solution:
L = 4.166... * 48 ≈ 200 m.

Verification / Alternative check:
At 4.166... m/s, 200 m takes 48 s, consistent with the overtaking duration.

Why Other Options Are Wrong:
50, 100, 150 m are inconsistent with the computed relative speed and given time.

Common Pitfalls:
Adding speeds (used for opposite directions) instead of subtracting for same direction.

Final Answer:
200 meters