Two trains 140 meters and 160 meters long are tracking on parallel routes in opposite directions at 40 km/h and 50 km/h respectively. How long do they take to clear each other? MCQ with Answer and Explanation
Two trains 140 meters and 160 meters long are tracking on parallel routes in opposite directions at 40 km/h and 50 km/h respectively. How long do they take to clear each other?
A. 15 seconds
B. 12 seconds
C. 14 seconds
D. 10 seconds
Answer: Option B
Solution (By JKExamLibrary)
Total distance = 140 + 160 = 300 meters. Relative speed = 40 + 50 = 90 km/h = 90 * (5/18) = 25 m/s. Time taken = 300 / 25 = 12 seconds.
A man can walk a distance in 4 hours and ride back in 3 hours. If he walks both ways, he takes 8 hours. How much time will he take if he rides both ways?
Explanation:
Let walking time one way be W and riding time one way be R. W + R = 7 hours. Walking both ways: 2W = 8 => W = 4 hours. Substituting W in first equation: 4 + R = 7 => R = 3 hours. Riding both ways: 2R = 2 * 3 = 6 hours.
Explanation:
Upstream speed = 16 / 4 = 4 km/h. Upstream Speed = Speed in still water - Current speed => 4 = Speed in still water - 1 => Speed in still water = 5 km/h.
A sedan tracks from location M to N at 50 km/h and manages the return tract to M at 70 km/h. What is the average speed recorded across the round journey?
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