Two trains 140 meters and 160 meters long are running at the speeds of 60 km/h and 40 km/h respectively in opposite directions on parallel tracks. What is the time taken by them to cross each other completely? MCQ with Answer and Explanation
Two trains 140 meters and 160 meters long are running at the speeds of 60 km/h and 40 km/h respectively in opposite directions on parallel tracks. What is the time taken by them to cross each other completely?
A. 9 seconds
B. 10 seconds
C. 12 seconds
D. 10.8 seconds
Answer: Option D
Solution (By JKSSB Mock Tests)
Total distance to be covered = 140 + 160 = 300 meters. Relative speed = 60 + 40 = 100 km/h = 100 * (5/18) = 250/9 m/s. Time = Distance / Speed = 300 / (250/9) = 300 * 9 / 250 = 10.8 seconds.
Explanation:
Let total distance be 90 km. First part = 30 km; Time = 30 / 30 = 1 hour. Remaining part = 60 km; Time = 60 / 60 = 1 hour. Total distance = 90 km, Total time = 2 hours. Average speed = 90 / 2 = 45 km/h.
Explanation:
Distance 1 = 50 * 3 = 150 km. Distance 2 = 60 * 2 = 120 km. Total distance = 270 km. Total time = 5 hours. Average speed = 270 / 5 = 54 km/h.
Explanation:
New speed = 5/7 of usual speed => New time = 7/5 of usual time. Difference = 2/5 of usual time = 24 minutes. 1/5 of usual time = 12 minutes => Usual time = 60 minutes.
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