2017 AMC 10 B

Complete problem set with solutions and individual problem pages

Problem 2 Easy

Sofia ran 5 laps around the 400-meter track at her school. For each lap, she ran the first 100 meters at an average speed of 4 meters per second and the remaining 300 meters at an average speed of meters per second. How much time did Sofia take running the 5 laps? (2017 AMC 10B Problem, Question#2)

  • A.

    5 minutes and 35 seconds

  • B.

    6 minutes and 40 seconds

  • C.

    7 minutes and 5 seconds

  • D.

    7 minutes and 25 seconds

  • E.

    8 minutes and 10 seconds

Answer:C

If Sofia ran the first 100 meters of each lap at 4 meters per second and the remaining 300 meters of each lap at 5 meters per second, then she took \dfrac{100}{4}+\dfrac{300}{5}=25+60=85 seconds for each lap. Because she ran 5 laps, she took a total of 5\cdot 85=425 seconds, or 7 minutes and 5 seconds.

The answer is \rm C.

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