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Average speed

Posted on: January 26th, 2014 by
5

Suppose a bicycle's average speed in any 10 minute interval is 18 miles per hour. How much distance will the bicycle travel in 25 minutes?

- via Australian Mathematical society Gazette puzzle corner


5 Responses to Average speed

  1. Mikey Baybee had this to say about that:

    We cannot know how far the bicycle traveled.

    Consider a bicycle which travels at exactly 18mph for 25mins, and another bicycle which alternates: 36mph for 5mins, resting stationary for 5mins, 36mph for 5mins, stationary for 5mins, 36mph for 5mins.

    Any ten minute interval has an average speed of 18mph for both bicycles, but the first bicycle will travel 7.5 miles, while the second will travel 9 miles.

    • Sid Hollander had this to say about that:

      You divide the 25 into Five intervals of 6 minutes each and had him rest in 3 of them and drive in only two of them, So he went 36mph for 10 min (i/6) of an hour. I.e 6 miles. To go 9 miles he couldn't have rested the last 5 minutes. Do you mean he averaged 26 for the last 5 minutes to get the other 3 to make the 9?

      • Sid Hollander had this to say about that:

        Oppps. 5 minutes each...but no matter. But I believe Logic/answer is not correct.

        • Mikey Baybee had this to say about that:

          I wrote "alternates: 36mph for 5mins, resting stationary for 5mins, 36mph for 5mins, stationary for 5mins, 36mph for 5mins".

          That's three intervals of cycling, two of resting.


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