SAT Subject Physics Practice Question 496: Answer and Explanation

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Question: 496

12. A bicyclist travels at a constant 25 km/hr for 30 minutes. He coasts for 15 minutes at a constant 20 km/hr and then pedals at a constant 40 km/hr for another 15 minutes. What was the average speed of the cyclist for the past hour?

A. 22.5 km/hr
B. 25 km/hr
C. 27.5 km/hr
D. 30 km/hr
E. 32.5 km/hr

Correct Answer: C

Explanation:

The correct answer is (C). During the first 30 minutes (1/2 hour) the bicyclist travels 12.5 km. The next 15 minutes (1/4 hour) the bicyclist travels 5 km, and during the last 15 minutes the bicyclist travels another 10 km. The total distance the bicyclist traveled during one hour is the sum of the three distances, which are 12.5 km + 5 km + 10 km = 27.5 km

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