I started teaching pi in reverse. I tell my students what the ratio is up front and then we see if we can measure a set of circles accurately enough in millimeters to reach that ratio.
Of course, they have this idea that they should have dessert pies for that day, so I created this worksheet that plays on the homophones.
To download a copy of the worksheet you see above, please visit the post "Are You Ready for Pi Day?" at Artistry of Education.