A train 400 m long running at 90 km/h enters a tunnel 800 m long. How long does it take to clear the tunnel completely?
Correct answer A. 48 seconds
Explanation
Speed = 90 × 5/18 = 25 m/s. It must cover 800 + 400 = 1200 m, so time = 1200 / 25 = 48 seconds.
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