Pi Day Pie Problems: Practice Geometry and Problem Solving!

What makes pi so deserving of an annual holiday? Your students probably don’t realize how incredible of a concept this mathematical constant actually is. Celebrate the greatness of approximately 3.14159 in your classroom on March 14 (3/14) in a way that makes math fun (and delicious) for your students!

Mathematicians have invented ways to figure out any of its infinity of digits, refining our real-world calculations in building and construction, quantum physics, air travel, medical procedures, space flight, and music theory (to name a few). You can connect the concept of pi to the real world by asking your students to “slice the pie,” an activity that will help them practice problem-solving thinking about geometry.

Easy as Slicing Pie!

What you need:

• Slice the Pie! (PDF file)
• Slice the Pie! Answer Key (PDF file)

What to do:

1. Draw a circle on the board. Ask students if they can see how to divide the circle into six equal pieces using three straight cuts.
2. Explain that it is possible to cut a pie into four, five, six, or seven pieces using three straight cuts. (The pieces will not be of equal size.)
3. Divide the class into groups of three or four. Hand out the Slice the Pie! worksheets. Have the groups work together to fill out the worksheets.
4. When the groups have had time to complete the worksheets, tell them that it is also possible to divide a pie into eight pieces by using three straight cuts. Challenge them to come up with a solution. (If the groups are stymied, you can hint that in order to cut a pie into eight pieces with three straight cuts, they would need to rearrange the pieces after the second cut.)
5. Have the groups share their solutions. (To cut a pie into eight pieces using three straight cuts, cut the pie in half with one cut. Cut the pie in quarters with the second cut. Stack the four pieces, one on top of the other, and cut through all four with the third cut.)

This Pi Day pie problems activity is ideal for Grades 3–5, but can easily be adapted for older or younger students. And for a helpful hint, you can gain obvious bonus points with your students by bringing in some actual pie to accompany your Pi Day activity! Every lesson is more fun when there are sweets involved. Enjoy!

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