A train runs at 36 km/h and crosses a standing man in 10 seconds. In how many seconds will it cross a platform 55 m long?

Introduction / Context:Crossing a man reveals the train length; crossing a platform requires covering train length plus platform length at the same speed. Convert consistently between units.

Given Data / Assumptions:

• Speed = 36 km/h = 10 m/s.
• Man-cross time = 10 s → train length L = 10 * 10 = 100 m.
• Platform length = 55 m.

Concept / Approach:Platform-cross time = (L + platform length) / speed.

Step-by-Step Solution:L = 100 m.Time over platform = (100 + 55) / 10 = 15.5 s.

Verification / Alternative check:At 10 m/s, 15.5 s covers 155 m, exactly train + platform.

Why Other Options Are Wrong:5.5, 6, 7.5 s are too short to cover 155 m at 10 m/s.

Common Pitfalls:Using only platform length instead of adding train length.

Final Answer:15.5 seconds