Difficulty: Medium
Correct Answer: 81 km/h
Explanation:
Given
Let train speed be v km/h, length L m.
L = (v − 4.5) × (5/18) × 8.4L = (v − 5.4) × (5/18) × 8.5Equate and solve ⇒ v = 81 km/h
Check (optional)
L = (81 − 4.5) × (5/18) × 8.4 = 178.5 m (consistent)
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