Pole crossing at 72 km/h – find length A train moving at 72 km/h crosses a pole in 15 s. What is its length?
Aptitude
Problems on Trains
Difficulty: Easy
Choose an option
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A150 m
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B200 m
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C300 m
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D350 m
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ENone of these
Answer
Correct Answer: 300 m
Explanation
Introduction / Context:The pole is a point obstacle; the entire train passes by, so distance equals the train length. Apply unit conversion and multiply speed by time to get the length.
Given Data / Assumptions:
- v = 72 km/h = 20 m/s.
- t = 15 s.
Concept / Approach:L = v * t after converting to m/s.
Step-by-Step Solution:
L = 20 * 15 = 300 mVerification / Alternative check:Reverse: 300 m / 20 m/s = 15 s, consistent.
Why Other Options Are Wrong:150 m, 200 m, 350 m: Each contradicts the exact multiplication result.
Common Pitfalls:Leaving units as km/h and seconds without conversion leads to wrong answers.
Final Answer:300 m