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Pi Day: Celebrating the mathematical constant π with a piece of pie and a good book.

Updated: Mar 18

What is π (pi)?

π is the mathematical constant that represents the ratio of the circumference of a circle to its diameter. It is an irrational number, which means that it cannot be expressed as a finite decimal or a fraction. Instead, it has an infinite number of digits that never repeat in any pattern.

Pi is one of the most important and ubiquitous mathematical constants, appearing in a wide range of fields, from physics and engineering to statistics and computer science. It is often represented by the Greek letter π (pronounced "pie").

When is Pi Day?

Pi Day is celebrated on March 14th (3/14), which corresponds to the first three digits of pi (3.14). This date was chosen by physicist Larry Shaw in 1988, who organized the first Pi Day celebration at the San Francisco Exploratorium. Since then, Pi Day has become a worldwide phenomenon, with events and activities taking place in schools, museums, and science centers.

Why is Pi Day Important?

Pi Day is not only a fun and delicious way to celebrate math, but it also serves as a reminder of the importance of mathematics in our daily lives. Pi is a fundamental constant that plays a crucial role in many scientific and technological applications, from designing bridges and buildings to calculating the orbits of planets and stars.

Moreover, Pi Day is an opportunity to promote math education and what better way to do that than by reading the book Sir Cumference and the Dragon of Pi.

Sir Cumference and the Dragon of Pi

This book by the very talented Cindy Neuschwander is a brilliant combination of literacy and numeracy. First printed more than 10 years ago in 1999 it is just as relevant and relatable now as it was then.

This book is part of a series of books about Sir Cumference his wife Lady Di of Ameter and their young son Radius. In this story Sir Cumference is accidentally turned into a dragon and Radius must try to find the correct potion to turn him back again as quickly as possible. The problem is that the doctor is away and the potion dose is measured using a riddle about circles, their radius and their circumference. Radius must solve the riddle to find the correct dose to save his father.

By working with his cousin Lady Fingers and Geo of Metry the Carpenter and Wheelright Radius discovers that the radius of a circle fits 3 and a bit times around the circumference of a circle. He just has to work out exactly what that extra “bit” is. By completing the tasks for this book your students can have fun learning this lesson for themselves and seeing why Pi is a decimal and what the closest fraction equivalent is. Activities for this book include drawing a dragon, finding the rule for the circumference of a circle, finding the circumference of circles, solving maths questions to solve a dragon related riddle, measuring circles to see what fraction of the diameter is required to create the diameter, drawing circles given the diameter, answering pi related questions and labelling parts of a circle to solve a riddle.


Pi Day is a unique celebration that combines math, science, and food in a fun and engaging way. By promoting math education and raising awareness about the importance of pi, Pi Day inspires curiosity, creativity, and critical thinking in people of all ages. Whether you're a math enthusiast, librarian or just love a good slice of pie, Pi Day is a wonderful occasion to celebrate the wonders of mathematics and the beauty of numbers.