Problem-Solving and Data AnalysisHardConverting a speed between unit systems
Problem-Solving and Data Analysis practice question
A cyclist travels at 72 kilometres per hour. What is this speed in metres per second? (1 kilometre = 1,000 metres; 1 hour = 3,600 seconds)
Answer: 20
Convert both units: 72 km/h = 72 × 1,000 metres per 3,600 seconds = 72,000 / 3,600 = 20 metres per second.
Common wrong answers
- If you answered 72000
- 72,000 is 72 × 1,000, the distance in metres per HOUR. It still needs dividing by 3,600 seconds.
- If you answered 259200
- 259,200 is 72 × 3,600, multiplying by the number of seconds. Going from 'per hour' to 'per second' DIVIDES by 3,600, since a second is a smaller time.
- If you answered 1.2
- 1.2 is 72 / 60, converting hours to minutes only. Seconds need a further division by 60, and the kilometres must become metres.
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