A car travels the first half of a distance at 60 km/h and the second half at 90 km/h. What is the average speed of the car for the entire journey?
Answer and explanation
Correct answer: B.
- Step 1: When distances are equal, average speed is the harmonic mean: .
- Step 2: Substitute values: .
- Step 3: Divide: .
Answer
72.0 km/h.
Why not the others: '' is the arithmetic mean , which ignores time weighting.
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