Pi Day (with minimal mention of digits)

Today, we celebrated our belated Pi Day! It was delayed due to inclement weather…


Though my #MTBoS friends were there to comfort me in my time of need!

Our spring trimester focus is always financial literacy. So, we spent most of last week researching recipes, planning for a shopping trip, going to the bank, shopping for ingredients, and making pies. Yes, I said it. We made pies for Pi Day, sue me! Now, finally the time had come to eat our pies, but first…we had to do some more math!

First we reviewed of some of the digits of Pi, highlighting that when rounded to the nearest hundredth it matches the numerical date of March 14th, which is subsequently known as “Pi Day” for this reason. I also wore my Pi shirt, which gives the students an opportunity to see that there are A LOT of digits in this number known as Pi and that I’m a nerd. We did, however, skip the traditional digit memorization activity for several reasons including working memory and tedious boredom.

Instead we estimated, explored, and discovered the circumference formula with our pies and some string.

I began by showing a video of the World Freehand Circle Drawing Champion, Alex Overwijk. Then, I modeled growth mindset by showing how I had not yet mastered the art of drawing the perfect circle.

I like to think this created the safe space allowing every student in my class to come up to the board and try their hand at public freehand circle drawing! Following some review/re-introduction of key circle vocabulary terms (diameter, circumference, and pi), we created a visual anchor chart on the board for students to reference as we continued our conversations about circles.

Taking inspiration from Christopher Danielson, I pre-cut some 9 inch strings that represented the diameter of our pie. The task was to work as a group to use the diameter string and observational skills to cut another string that showed each student’s estimate of the circumference of our pie. Some estimates were initially too small, some were initially too big, but eventually most students made reasonable estimates.

Finally, the direct instruction was differentiated for different groups of students. Some groups received a concrete demonstration that showed just over three diameter strings would complete the circumference of the pie and then were able to use calculators to multiply 9 x 3.14. Other groups saw the inverse property of division and multiplication and reasoned that since the circumference divided by the diameter equals pi; then pi times the diameter would equal the circumference. This group of students was able to do the circumference calculations without calculators.

Here are some pictures of their work!

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Oh, I almost forgot, after all this we ate the pie! Talk about some sweet extrinsic motivation!

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