Trains — clearing time when two trains approach each other: Two trains 512 m and 528 m long run towards each other at 84 km/h and 60 km/h. From the moment they meet, in how many seconds will they clear each other completely?
Verbal Reasoning
Problems on Ages
Difficulty: Easy
Choose an option
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A26 s
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B25 s
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C15 s
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D27 s
Answer
Correct Answer: 26 s
Explanation
Introduction / Context:This is a standard relative-speed problem for trains moving in opposite directions. The time to completely cross equals (sum of lengths) / (relative speed).
Given Data / Assumptions:
- Lengths: 512 m and 528 m.
- Speeds: 84 km/h and 60 km/h in opposite directions.
Concept / Approach:Convert speeds to m/s, add them to get relative speed, add train lengths, then compute time = distance / speed.
Step-by-Step Solution:
Relative speed = 84 + 60 = 144 km/h.Convert: 144 km/h = 144 * 1000 / 3600 = 40 m/s.Total distance to clear = 512 + 528 = 1040 m.Time = 1040 / 40 = 26 s.Verification / Alternative check:
Units check: meters divided by meters/second gives seconds; numbers consistent.Why Other Options Are Wrong:
- 25 s, 15 s, 27 s are inconsistent with the computed 26 s.
Common Pitfalls:
- Forgetting to convert km/h to m/s correctly (multiply by 5/18).
- Using difference of speeds instead of sum for opposite directions.
Final Answer:26 s