Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: How do I find the average speed for this problem?

  1. Sep 9, 2011 #1
    1. The problem statement, all variables and given/known data
    I don't know how to start.. someone please give me a step-by-step explanation.
    Julie drives 100 mi to Grandmother's house. On the way there she drives half of the distance at 42 mi/hr and half the distance at 68 mi/hr. What is Julie's average speed (in mi/hr) on the way to Grandmother's house?


    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Sep 9, 2011 #2

    NascentOxygen

    User Avatar

    Staff: Mentor

    You know the total distance, so you need to work out the total time taken. To do this, work out the travel time on each different section, and then add them up.

    If you do it this way, you'll avoid falling into the trap !! :smile:
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook