Average Speed

QUESTION:

A motorist wishes to travel 40 kilometers at an average speed of 40 km per hour. During the first 20 kilometers, an average speed of 40 km/h is maintained. During the next 10 kilometers, however, the motorist goofs off and averages only 20 km/h. To drive the last 10 kilometers and average 40 km/h, the motorist must drive

1. 60 km/h.
2. 80 km/h.
3. 90 km/h.
4. faster than the speed of light.

For help with this question, see Conceptual Physics, Chapter 2.

Check your answer.

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