Equal train and platform lengths – find train length A train and platform have equal lengths. The train runs at 90 km/h and crosses the platform in 1 minute. Find the train length.
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A500 m
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B550 m
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C600 m
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D750 m
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ENone of these
Answer
Correct Answer: 750 m
Explanation
Introduction / Context:When train and platform lengths are equal, the total crossing distance is twice the train length. Convert the speed to m/s and multiply by time to get the total distance, then halve it.
Given Data / Assumptions:
- Speed = 90 km/h = 25 m/s.
- Crossing time = 60 s.
- Train length = platform length.
Concept / Approach:Total distance D = v * t. With equal lengths, D = L + L = 2L, so L = D / 2.
Step-by-Step Solution:
D = 25 * 60 = 1500 mL = D / 2 = 1500 / 2 = 750 mVerification / Alternative check:Reconstruct: Train 750 m + platform 750 m = 1500 m in 60 s at 25 m/s — consistent.
Why Other Options Are Wrong:500 m, 550 m, 600 m: When doubled, these do not yield the 1500 m total distance implied by the given speed and time.
Common Pitfalls:Forgetting to double the train length when platform length equals train length; or keeping speed in km/h with seconds.
Final Answer:750 m