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Homework Help: Finding average speed & distance traveled?

  1. Sep 28, 2009 #1
    1. The problem statement, all variables and given/known data

    Sally travels by car from one city to another. She drives for 30.0 min at 52.0 km/h, 35.0 min at 48.0 km/h, and 23.0 min at 50.0 km/h, and she spends 10.0 min eating lunch and buying gas.

    2. Relevant equations

    avg. speed= distance traveled / time of travel

    3. The attempt at a solution

    first, I added all three speeds (52+48+50) and divided by 3. I got 50 as the average speed, but the website says I'm incorrect.

    How can I find the average speed without the distance traveled?

    avg. speed = distance traveled / (30+35+23)
    avg. speed = distance traveled / 88
  2. jcsd
  3. Sep 28, 2009 #2


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    Homework Helper

    I don't think you can find the average speed without first finding the distance!
    It shouldn't be hard to work out the distances - just use d = vt for each. Get the total distance and the total time, then use the "relevant equation".
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