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Average Speed between two cities

  1. Sep 9, 2014 #1
    Pauline travels between two cities. First she drives for 31 minutes at an average speed of 82 km/hr then for 23 minutes at an average speed of 51 km/hr, then she spends 25 minutes eating lunch and buying gas, and then she drives for 15 minutes at an average speed of 44 km/hr.

    Find Pauline’s average speed for this trip. Express it in kilometers and round your answer to the nearest kilometer

    I know I have to use the average speed formula, which is total distance/time (94 minutes in this case). How do I get the time taken from 31 minutes at an average speed of 82km/hr, etc...?
     
  2. jcsd
  3. Sep 9, 2014 #2

    BvU

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    Hello Chiffy, and welcome to PF. Posting a question means filling in the template.
    1. The problem statement, all variables and given/known data
    Pauline travels between two cities. First she drives for 31 minutes at an average speed of 82 km/hr then for 23 minutes at an average speed of 51 km/hr, then she spends 25 minutes eating lunch and buying gas, and then she drives for 15 minutes at an average speed of 44 km/hr.
    Find Pauline’s average speed for this trip. Express it in kilometers and round your answer to the nearest kilometer
    Expresssing a speed in kilometers is going to be very impossible. perhaps they want kilometers per hour ?
    2. Relevant equations
    average speed formula, which is total distance/time

    3. The attempt at a solution
    oops. Something like: I have total time, now all I need is total distance. That is distance covered in first 31 min plus distance .. etc.


    Not so difficult, right ? Except for the last part, perhaps.

    Your question:
    Is answered with: "31 minutes" etc.

    Not what you hoped for, I suppose. Perhaps you want the distance ? 1 hour 82 km, 2 hours 2 * 82 km, 1/2 hour: 1/2 hour * 82 km/hour = 41 km. Recognize the pattern ?
     
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