Problems on Trains – Time to cross a platform (sum of lengths): A 280 m train moves at 60 km/h. How long will it take to cross a 220 m platform completely?

Introduction / Context:Total distance to clear the platform equals train length + platform length. With constant speed, time equals distance divided by speed (in consistent units).

Given Data / Assumptions:

• L_train = 280 m.
• L_platform = 220 m.
• Speed = 60 km/h = 16.666… m/s.

Concept / Approach:Time = (L_train + L_platform) / speed_in_mps.

Step-by-Step Solution:Distance = 280 + 220 = 500 m.Speed = 60 * (1000/3600) = 16.666… m/s.Time = 500 / 16.666… = 30 s.

Verification / Alternative check:In 30 s at 16.666… m/s, distance = 500 m, exactly the needed sum of lengths.

Why Other Options Are Wrong:20, 25, 35, 28 s contradict D/v with correct unit conversion.

Common Pitfalls:Forgetting to add both lengths; using 60/3.6 incorrectly.

Final Answer:30 seconds