Two trains of equal length cross a pole in 12 seconds and 18 seconds respectively. If the length of each train is 180 meters, find the time taken by them to pass each other when running in opposite directions. MCQ with Answer and Explanation
Two trains of equal length cross a pole in 12 seconds and 18 seconds respectively. If the length of each train is 180 meters, find the time taken by them to pass each other when running in opposite directions.
A. 14.4 seconds
B. 15.6 seconds
C. 13.2 seconds
D. 16.0 seconds
Answer: Option A
Solution (By JKSSB Mock Tests)
Speed of first train = 180 / 12 = 15 m/s. Speed of second train = 180 / 18 = 10 m/s. Total distance to cross = 180 + 180 = 360 meters. Relative speed in opposite directions = 15 + 10 = 25 m/s. Time taken = 360 / 25 = 14.4 seconds.
A man covers 3/5 of his journey at 60 km/h, 1/4 of his journey at 40 km/h and the remaining journey at 20 km/h. Find his average speed for the whole transaction.
Explanation:
Let total distance be 400 km. First part = 240 km; Time = 240/60 = 4 hours. Second part = 100 km; Time = 100/40 = 2.5 hours. Remaining distance = 400 - 240 - 100 = 60 km; Time = 60/20 = 3 hours. Total time = 4 + 2.5 + 3 = 9.5 hours. Average speed = 400 / 9.5 = 4000 / 95 = 46.15 km/h.
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