3.14... We all know the number. You probably took a stab at memorizing it in some math class long ago but the practically infinite number of digits proved to be a challenge. I personally never made it past 3.1415. Nevertheless, we can still enjoy Pi day to its fullest, even though our memories have failed us.
In my years as an educator, I found that food was a great motivator, no matter the age of the student! If you promise a slice of pie at the end of an activity, you can get a student to learn just about anything. When it comes to understanding Pi though, it really is pretty easy. All they need to know to start is that Pi is a circle's circumference (the measurement of the outside) divided by the diameter (the measurement down the middle from one side of the circle to the other) and you're going to prove that by testing it. Whether you're at home or in a classroom, you probably have plenty of things that are shaped like circles. From cake pans to the lids on glue sticks, gather 4 to 5 examples of circles of all different sizes. Measure the circumferences and diameters of each object and then divide them. Depending on the ages of your students, it might be best to just do this on a calculator. Your goal is simply to prove that every time you divide a circle's circumference by it's diameter, you will get a number that is suspiciously close to 3.14. Easy as pie!
For your last circle to check for Pi, make your own pudding pie. You can use any flavor of pudding and add the designated amount of milk in it. Tip: Using sweetened condensed milk gives it a sweet custard like taste and texture. Pour the pudding and milk mixture into the pie crust and let it solidify in the refrigerator. You can then add whipped cream, fruit, nuts or chocolate on top to decorate. Before you enjoy a slice, take one last measurement of the circumference and the diameter of the pie and divide away. Pi never tasted so good!
And if you want to continue the learning, check out these books about measurement.