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.
Aptitude
Problems on Trains
Difficulty: Easy
Choose an option
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A420 m
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B500 m
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C300 m
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D250 m
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ENone of these
Answer
Correct Answer: 300 m
Explanation
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:
D = (60 * 1000 / 3600) * 30 = 16.666... * 30 = 500 mPlatform = 500 - 200 = 300 mVerification / 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