Pole crossing – length from speed and time A train takes 9 s to cross a pole at 48 km/h. What is the train length?

Difficulty: Easy

Correct Answer: 120 m

Explanation:


Introduction / Context:
When crossing a pole, the distance covered equals the train’s length. Convert speed to m/s and multiply by time to get length directly.


Given Data / Assumptions:

  • v = 48 km/h = 13.333... m/s.
  • t = 9 s.


Concept / Approach:
L = v * t with consistent units.


Step-by-Step Solution:

L = (48 * 1000 / 3600) * 9 = 13.333... * 9 = 120 m


Verification / Alternative check:
At 13.333... m/s, 9 s gives exactly 120 m. Checks out.


Why Other Options Are Wrong:
150 m, 90 m, 80 m: Do not match the computed product.


Common Pitfalls:
Not converting km/h to m/s. Using 48 as m/s leads to large errors.


Final Answer:
120 m

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