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Pi Day is coming up next week on March 14 (3/14), chosen because the first three digits of pi are 3.14... It is a fun way to celebrate the mathematical constant π and all things math.

Pi is based on the relationship (ratio) between circumference of a circle and its diameter. If you're a bit rusty in math, the diameter is a straight line segment that passes through the center of a circle and has endpoints on the circle. The circumference is the distance around the outside of the circle.

Public domain image by Kjoonlee, based on previous work by w:User:Papeschr at  Wikimedia

Pi was first established as the ratio of the circumference to the diameter.

π = C/d

It is a fascinating number because it is so useful, but it is also irrational. That means it is an infinite, non-repeating decimal.

Pi Day activities can run the gamut from serious to seriously lighthearted.

Public domain image of a Pi Day pie

You might want to check out

One great way to celebrate Pi Day is to read a book about math. We maintain a list of children's math books for Pi Day and every day at Science Books for Kids. Let's add some recent releases to the list:

Goodnight, Numbers by Danica McKellar and illustrated by Alicia Padron is for children who are learning their numbers.

Danica McKellar is not just another celebrity using their fame to hawk children's books. She is a serious mathematician whose goal is to get kids excited about math through books and videos. Her first books were for middle and high school aged kids. Now she's writing for the youngest set.

You can see what she has to say in this book trailer:

Age Range: 2 - 5 years
Publisher: Crown Books for Young Readers (March 7, 2017)
ISBN-10: 110193378X
ISBN-13: 978-1101933787

STEAM stands for science, technology, engineering, art, and math.  This is Not Another Math Book by Anna Weltman and ilustrated by‎ Charlotte Milner is a perfect choice for older kids who want to explore art as a way to understand math.

Author Anna Weltman has created an imaginative series of hands-on projects that include exploring symmetry by drawing kaleidoscopic patterns, growing a forest of fractal trees, and assembling five-square pentomino shapes into pictures.

Ages: 9+
Paperback: 96 pages
Publisher: Kane Miller Books / EDC Publishing; First American edition (2018)
ISBN-10: 1610675975
ISBN-13: 978-1610675970

For the full list, see children's math books for Pi Day and every day at Science Books for Kids.