As if you needed a reason to celebrate a mathematical concept, today is Pi Day (3/14 – get it?). So why is this important? (I have to use the Greek Pi, as opposed to the symbol in the blog). There aren’t many activities here, but mostly a shout out to Pi (and those who shout out for it).

- Pi shows the relationship between diameter and circumference of a circle.
- Pi is a constant – no matter what size the circle, as a ratio, its value remains the same.
- Pi is known mostly as 3.14, but it has been calculated out to over a trillion digits.
- Pi has a long history: it comes from the Greek letters and the Egyptians used the equivalent of Pi/2 for their proportions of the pyramids – this seems to have been a good choice, if longevity plays into architecture….
- It is central in equations for area of a circle and volume of a cylinder (central to those of us who like curling and cans of soup).
- Is Pi a normal number?
- Are people who wear a Pi t-shirt normal? Lots to think about.
- Are there any other constants that have (or should have) a day?

**Resources: **

- Pi Day Website – Learn about Pi
- Wikipedia explanation with cool animation that actually makes the concept understandable! (This would be a great experiment to recreate. Give students four or five circles (lids, etc) of different diameters. Measure the diameter of each, mark a spot on the circle and roll it out, then measure the circumference (or use measuring tape). Is the circumference 3.14 x the diameter? Have them record their findings on a chart.

**Enciendalo!**