Math Mondays: Pi Day Blog Hop

Pi Day is just two weeks away.  It's a Monday, so I am planning it now so that we can kick off the week with some fun.  Read on for ideas of what I am planning, but first, some fun Pi Day Facts:

  1. Pi is the most recognized irrational number in the world.
  3. The symbol for pi (π) has been used regularly in its mathematical sense only for the past 250 years.


Pi Day is a great day to play with irrational and rational numbers.  First, we talk a little about the definition of irrational numbers and rational numbers. 

  • Rational numbers are real numbers that can be written as a fraction such as 3, 3/4, 1.57, 3.66666666  or we can think of them as: integers, decimals that repeat or decimals with that terminate (i.e. end).
  • Irrational numbers is a real number that can't be written in fraction form.  I think of them as decimals that never repeat.  Some of the more famous irrational numbers include pi, the square root of two and e (Euler's number).  See some examples here (scroll down the page).

Mathsteps has a pretty good diagram of how rational and irrational numbers fit in the big scheme of numbers here.

After a brief discussion, we get down to business "showing" an irrational number of our choice.  I give students three options: beads, paper chains, and cityscapes to represent irrational numbers. 

To make the beaded necklaces, students take a variety of beads (you need at least 10 unique beads) and set up a code for each color/shape as a representative of a number.
In the photo above, you can see that there is a round purple bead for 5, an orange bead for 9, etc.

Each student selects an irrational number to make such as pi or root 2. Students string the beads on a string in the order of the numbers of the irrational number.  I let the students decide how many beads (numbers) to put on but give a minimum of 25.  Last year one of the students said upon finishing her necklace: "I'm wearing Pi".  Another student reflected that now she completely understands what it means when a number is an irrational number versus a rational number.  The cityscapes and paper chains are great fun as well and employ similar principals.  Get a full set of the activities here.  

For other great ideas for Pi Day, check out the posts from fellow teacher-bloggers below.




  1. Clearly we love the same Pi Day joke! ;) Neat hands-on activity - thanks for sharing!

  2. Love all the quick Pi Day Trivia facts. I like to challenge my students to find a unique fact each year. We also make beads of 100 digits Pi, e, or Root 2! It's a day of math fun.

  3. I like the beads activity, that's a great way to make it concrete for kids. Your discussion of rational and irrational numbers put in mind the fact that pi is a transcendental number (not a root). And even though the number line seems crammed full of rational numbers and irrational roots, almost all numbers are transcendental, by virtue of transcendental numbers being uncountable. So cool! Thanks for the post!