Train A (120 meters long) moving at 72 km/h overtakes Train B (180 meters long) moving in the same direction on a parallel track at 54 km/h. How many seconds does it take Train A to completely clear Train B?
Answer and explanation
Correct answer: B. 60 seconds
- Step 1: Relative speed = 72 - 54 = 18 km/h. Step 2. Convert to m/s: 18 (1000/3600) = 18 (5/18) = 5 m/s. Step 3. Total distance to completely clear = Length A + Length B = 120 + 180 = 300 meters. Step 4. Time = 300 / 5 = 60 seconds. Answer: 60 seconds, dividing total clearance distance 300 meters by relative speed 5 m/s. Why not the others: 45 seconds only clears Train B (180/5 = 36) or Train A; 300/5 = 60 seconds.
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