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Homework Help: Distance, time, speed

  1. Aug 20, 2014 #1
    1. The problem statement, all variables and given/known data
    Mac walked to a park from the college at 5 km/h. 10 minutes later, Steve started riding his bike at 15 km/h to the same park to meet Mac. They arrive at the same time at the park. How far is the park from the college?

    2. Relevant equations
    Rate = D/t

    3. The attempt at a solution
    I know Steve is travelling 10km/h faster than Mac. I also found the km traveled by Mac which was (5/6)km. and then found the time at which steve took to reach (5/6)km.... but i have a feeling this is totally wrong

    please help?
  2. jcsd
  3. Aug 21, 2014 #2

    Ray Vickson

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    You need to show your work, so that we can tell where you went wrong.
  4. Aug 21, 2014 #3


    Staff: Mentor

    Steve and Mike are covering the same distance, with distance as rate * time. Write expressions for the amount of time each guy is travelling. The distance you came up with, 5/6 km, is wrong.
  5. Aug 21, 2014 #4


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    No, it is not wrong, but you have to explain what you mean.

    Mac is at distance of 5/6 km away when Steve starts. With respect to Mac, Steve had to cover 5/6 km with speed 10 km/h. You use a frame of reference fixed to Max. In that frame of reference, Max does not move, and Steve moves with 10 km/h.

    Go ahead!

  6. Aug 24, 2014 #5
    The original post does not state that Steve and Mike started at the same place. Thus, we cannot assume that they are the same distance from the park in their travels.
  7. Aug 24, 2014 #6

    Ray Vickson

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    That makes the problem un-doable. I would guess they are supposed to be starting from the same point, whose distance to the park is sought.
  8. Aug 25, 2014 #7
    The solution of the park's "distance" from the college could be expressed as a function depending on the biker's distance. You would just have to stop there, or show a graph of possible and reasonable solutions. The solution would be "distance" according to the walker's path.

    Even if you assume that the walker and the bicyclist started at the same location, the problem as stated does not indicate that they took the same path.
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