A 120 m long train crosses a pole in 10 seconds. What is its speed in km/h?
Aptitude
Problems on Trains
Difficulty: Easy
Choose an option
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A40 km/h
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B43.2 km/h
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C45 km/h
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DNone of these
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E36 km/h
Answer
Correct Answer: 43.2 km/h
Explanation
Introduction / Context:Crossing a pole uses the train’s own length as the distance. Convert the resulting m/s speed to km/h for the final answer.
Given Data / Assumptions:
- L = 120 m.
- t = 10 s.
Concept / Approach:v_mps = L/t = 120/10 = 12 m/s; v_kmph = v_mps * 3.6.
Step-by-Step Solution:
v_mps = 12 m/s.v_kmph = 12 * 3.6 = 43.2 km/h.Verification / Alternative check:Reverse: 43.2 km/h = 12 m/s; in 10 s it covers 120 m—exact train length.
Why Other Options Are Wrong:36 or 40 km/h underestimates; 45 km/h overestimates; “None of these” is false because 43.2 km/h matches.
Common Pitfalls:Using 18/5 incorrectly; rounding 43.2 to 45.
Final Answer:43.2 km/h