Two trains 120 meters and 180 meters long are running in opposite directions at speeds of 42 km/h and 48 km/h respectively. In what time will they cross each other? MCQ with Answer and Explanation
Two trains 120 meters and 180 meters long are running in opposite directions at speeds of 42 km/h and 48 km/h respectively. In what time will they cross each other?
A. 14 seconds
B. 10 seconds
C. 16 seconds
D. 12 seconds
Answer: Option D
Solution (By JKSSB Mock Tests)
Total distance = 120 + 180 = 300 meters. Relative speed in opposite directions = 42 + 48 = 90 km/h = 25 m/s. Time taken = 300 / 25 = 12 seconds.
Explanation:
Let stream speed be c. Upstream speed = 12 - c, Downstream speed = 12 + c. Given: 2 * (12 - c) = 12 + c => 24 - 2c = 12 + c => 3c = 12 => c = 4 km/h.
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