Bringing Lessons to Life

Have your students ‘walk the graph’

Problems that begin with “A car traveling 50 miles an hour leaves Chicago ... ” are the bane of many algebra students. Here’s a great way to help your students visualize and make sense out of those problems:

1. Push all the desks to the edge of the room. Using duct tape, mark a line along one wall. Call that the distance line (or x axis). If a car started on this line, where would it finish? (The other end of the room.) Mark off intervals representing distance—25 miles, 50 miles, 100 miles and so on.
2. Place a second strip of duct tape perpendicular to the first. Call this the time line (or y axis). Mark off intervals representing time—30 minutes, one hour and so on.
3. Ask for a volunteer to be the “driver” of your car. Position that student where the two lines intersect.
4. Remind students to consider:
   • Where does the car start?
   • Which direction is it heading?
   • How fast is it going?
5. Have the student “walk the graph.” (Have one second of class time represent one minute.)

Where is the car after 30 minutes? One hour? How long does it take to reach the destination?

Now move on to a more complex problem. Suppose one car begins at the starting point, but another car begins 25 miles behind it. The first car travels at 50 miles per hour, the second at 60 miles per hour. When will the second car overtake the first?

Once students have seen these problems acted out, they can understand the graphs they create.

Reprinted with permission from the March 2007 issue of Better Teaching® (Secondary Edition) newsletter. Copyright © 2007 The Teacher Institute®, a division of NIS, Inc. Source: Jennifer Printz, “The Buggy Lab: Comparing Displacement and Time to Derive Constant Velocity,” School Science and Mathematics, May 2006 (979-862-8100, www.ssma.org).