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Increasing speed by 5 mph saves 10 mins?

  1. Nov 8, 2006 #1
    If a person drives the same distance twice, and saves 10 mins by driving 5mph more the second time, what is the distance and the speeds?
     
  2. jcsd
  3. Nov 8, 2006 #2

    chroot

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    Staff Emeritus
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    Speed * time = distance.

    Set up two equations -- one for each trip -- and notice that the distances are equal. Thus, you can set the equations equal to each other, arriving at:

    Speed1 * time1 = speed2 * time2.

    You know that speed2 = speed1 + 5, and that time2 = time1 - 10.

    Put these equations together and solve for distance...

    - Warren
     
  4. Nov 8, 2006 #3
    Can you work through it for me? I keep getting time1=10+2*speed1...
     
  5. Nov 9, 2006 #4

    berkeman

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    Staff: Mentor

    Write out your full two equations and show how you are trying to solve them.
     
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