A man crosses a straight 600 m street in 5 minutes at constant pace. What is his speed in km/h?
Aptitude
Time and Distance
Difficulty: Easy
Choose an option
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A7.2 km/h
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B3.6 km/h
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C10 km/h
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D8.4 km/h
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E6.0 km/h
Answer
Correct Answer: 7.2 km/h
Explanation
Introduction / Context:Convert a meters-per-minute rate to km/h by appropriate unit conversions (m → km, min → h).
Given Data / Assumptions:
- Distance = 600 m.
- Time = 5 minutes.
Concept / Approach:First compute m/s or m/min, then convert to km/h. 1 m/s equals 3.6 km/h.
Step-by-Step Solution:
Speed = 600 m / 5 min = 120 m/minConvert to m/s: 120 / 60 = 2 m/sConvert to km/h: 2 * 3.6 = 7.2 km/hVerification / Alternative check:Direct conversion: 0.6 km in 1/12 h → 0.6 * 12 = 7.2 km/h.
Why Other Options Are Wrong:They reflect wrong conversion factors between m/s and km/h, or minutes-to-hours errors.
Common Pitfalls:Using 3.0 instead of 3.6 for the m/s to km/h factor; forgetting to divide by 60 to get m/s.
Final Answer:7.2 km/h