Something interesting happened to me recently. I was invited by the PISA team to attend the OECD in Paris and discuss possible avenues for further data analysis, drawing from their giant and fascinating data set of 15 million students worldwide. I sat at the table with the team on the first morning and the first question the director asked me was:

### What is going on with Americans and π?

This seemed like a funny question but I later learned that US students do exceptionally poorly on all of the PISA test items in which they have to use their knowledge of π.

My first thought in answering this question was that the US celebrates Pi day with great enthusiasm and gusto but a primary focus of the day is on memorizing digits. It seems there are many more students in the US who can tell you digits in π than there are students who know what π means.

I understand that memorizing π digits can be made into an engaging activity, with fun filled competitions, but I also worry that it feeds into an already dominant idea in the US that math is about the memorization of numbers. I also worry that too few students have any idea of what π means.

This is somewhat ironic as π is actually a really cool number, not, in my view, because of the length of the digits that can be memorized, but because it is the number that emerges when the circumference of any circle or sphere – in the world – is divided by twice its radius. Any circle or sphere in the World!! – whether it be a pea or the whole earth. Now that is cool!

So I prefer π day to be about activities that help students understand the meaning of π. In my student online class, that has been watched by over 100,000 students now, there is a small whiteboard animation that conveys the meaning of π that you might like to use in π day.

### If you would like ideas for celebrating Pi and what it means here are some great ideas for activities that we have found:

exploratorium

piday

pinterest

ams

purdue

And if you would like to give your students a π challenge, here is one of the PISA questions that was very demanding for students across the world, not just in the US. It is a question that requires students to engage in some mathematical modeling, and to use π in finding a solution. Only 4% of 15 year olds and 2% of US 15 year olds could solve this question. So it is a great one for students to work on together in groups, and experience their brains growing!

A full analysis of this question and the students’ mathematical strengths and weaknesses in the US can be read here.

http://oecd.org/pisa/keyfindings/PISA2012_US%20report_ebook(eng).pdf

And this is a new publication from PISA on the gender differences they found in the tests, which they show to be due to confidence and learning approaches:

http://oecd.org/pisa/keyfindings/pisa-2012-results-gender.htm

The paper I presented at the White House gives insights into the same phenomenon.

Youcubed-STEM-white-house.pdf

This π day is very special, on Saturday the date is 3/14/15 or to put in another way 3.1415! This happens once every century, so it is definitely a day to celebrate. And when the time is 9.26.53 we can celebrate the date and time being the first 10 digs of π. I hope you enjoy your π day and share with us the great activities you use.