- 1 lb bags of Skittles or M&Ms (one bag should be enough for about 5 pairs of students, so figure 2 bags for a class of 20-25 students)
- paper plates (1 per pair)
- paper towels or napkins (1 per pair)
- small plastic cups (1-2 per pair)
- Create a table with two columns: Trial and Number of Candies Left.
- Pour out your candy onto the plate and count all of them. Record this as Trial 0 in your table.
- Put all the candy back into the cup. Pour out the candy onto the plate again, but this time only count the ones that are face up--that is, have the "s" or "m" showing. Record this in your table.
- Put only the candies that were face up back into the cup. Remove all of the candy that was face down--you can eat those now.
- Repeat steps 3 and 4 until you have no candy left.
- On a coordinate plane, plot your data as coordinate points. (Ask yourself, "Which is the independent and dependent variable in this experiment?" Your answer will help you decide how to graph the data.) What do you notice about the graph this data creates?
What happens in this activity is an example of exponential decay. When your students plot the data as coordinate points on a graph, they'll see an exponential curve. This doesn't even really require fiddling around with Stat Plot on a TI graphing calculator, although they can use it to help create an exponential function that fits the data they found as a final step (or extension).
I based my graphic organizer on this Exponential Functions module from Kennesaw State University's Transitions Project, a website designed for teachers in training and obviously worth exploring for everyone else. The only thing I really added to their worksheet was a coordinate plane for students to use to graph the data.