A train covers 90 metres while passing a standing man. What is the length of the train (in metres)?

Introduction / Context:
When a train passes a stationary point or a standing man, the distance traversed while completely passing equals the length of the train itself (the man has no effective length to add).

Given Data / Assumptions:

• Distance covered while passing the man = 90 m.
• Man is stationary (length negligible for this context).

Concept / Approach:
Distance to pass a point object = train length. Therefore, the measured distance of 90 m equals train length directly.

Step-by-Step Solution:

Verification / Alternative check:
Had it been a platform of length P, we would need L + P; here P = 0, so the observed 90 m is L.

Why Other Options Are Wrong:
20, 71, 87, 100 m do not match the given traversal distance for passing a point object.

Common Pitfalls:
Confusing post/man cases with platform/bridge cases where extra length is added.

Final Answer:
90 m