Teaching Exponential Decay with Candy

Motivating students to learn mathematics can be a challenge. However, this activity is sure to be a hit with your students. I used the activity below in my 8th grade mathematics class to illustrate an exponential decay relationship. By having the students remove the pieces of candy which land with the marked side up, they unknowingly collect data representing an exponential decay pattern. Students can evaluate this data in graph and table form to further study characteristics such as decay factor and initial value. This activity works with M&M's, Skittles or any candy that is marked on one side. If students have food allergies, pennies can be substituted.

************************************************************************************
Activity Directions:
1) Please wash your hands or use hand sanitizer before doing this activity. You need to have clean hands before starting this activity.

2) Form small groups of 4-5 people.

3) Please get the following materials:
• One metal tray
• 2 blue cups
• Bag of M & M’s

4) Count the M&M’s in your bag, and ensure that a "m" is stamped on each M&M. Non-visible m’s can be exchanged. You should have a 100 M&M’s in your bag.

5) Each person should record the data for this activity in the following table:



6) Each group is to shake their cup and spill their M-&-M's into their tray. Count the number of M-&-Ms that land "m"-side-up, then remove them from the tray and place them in a "holding" cup. Use the table above (labeled "# Spills", "# M-side-up", and "# Remaining"), record the appropriate numbers. Put the remaining M & Ms back into the shaking cup.

7) Repeat this cycle of spilling the candies into the tray, counting and removing those pieces that land M-side-up. Record the number removed until there are no candies left.

8) Graph spill number versus total number of M&M’s (Spill #, Total # M&M’s) on graphing paper.


9) Please answer the following questions:

A.) What type of function best fits your data (i.e. linear, exponential growth, or other?) and why?

B.) Please write the general equation for the function you selected above.

C.) What is the initial value?

D.) What is the decay factor?

E.) Please write the equation of the graph model (i.e. equation that best fits your collected data)


10) What did you learn doing this activity?

11) What questions do you still have?