Train + platform – compute platform length A train at 60 km/h crosses a platform in 30 s. If the train length is 200 m, find the platform length.

Introduction / Context:We know speed and crossing duration; compute total traverse and subtract the known train length to isolate the platform length.

Given Data / Assumptions:

• v = 60 km/h = 16.666... m/s.
• t = 30 s.
• L_train = 200 m.

Concept / Approach:Total distance D = v * t = train + platform → platform = D - train.

Step-by-Step Solution:

Verification / Alternative check:At 16.666... m/s, 30 s gives 500 m, consistent with 200 m + 300 m.

Why Other Options Are Wrong:420 m, 500 m, 250 m: Do not satisfy D = v * t with the train length provided.

Common Pitfalls:Rounding 16.666... too early; however, the final arithmetic resolves cleanly to 300 m.

Final Answer:300 m