Problem-Solving and Data AnalysisVery hardAverage speed over two legs
Problem-Solving and Data Analysis practice question
A driver covers the first 90 kilometres of a trip at an average speed of 60 kilometres per hour and the next 90 kilometres at an average speed of 90 kilometres per hour. What is the driver's average speed, in kilometres per hour, for the whole 180 kilometres?
Answer: 72
The legs take 1.5 h and 1 h, so 180 km ÷ 2.5 h = 72 km/h.
Common wrong answers
- If you answered 45
- 45 halves 90.
- If you answered 75
- 75 averages the two speeds, ignoring that the slower leg takes longer.
- If you answered 150
- 150 adds the speeds.
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