# π (Pi) Approximation Day

By Lindsay Roseberry, Reference Department Pi Approximation Day is always celebrated on July 22; this year it’s on a Friday. Why you ask? Because the fraction 22/7 is used as a common approximation of π. The number π is a mathematical constant that is the ratio of a circle’s circumference to its diameter and is approximately equal to 3.14159…. π (Pi) Day is celebrated by mathematicians, geeks and everyone else on March 14—3.14, get it?) It has been represented by the π, a Greek letter for P and pronounced pi, since the mid-18th century. Because π is an irrational number, it can’t be shown as a fraction, such as ½, ¼ or 3/16. Consequently, its decimal representation never ends and never settles into a permanent repeating pattern.

A fraction represents a part of a whole or, more generally, any number of equal parts, describing how many parts of a certain size there are, for example, one-half, eight-fifths, three-quarters. A simple fraction consists of an integer numerator, displayed above a line (or before a slash), and a non-zero integer denominator, displayed below (or after) that line. An approximation is a mathematical and scientific term used to describe anything that is very near to but not exactly equal to something else. (In English, we’d use the word roughly or almost.)

Want to celebrate π Approximation Day?

Eat pie, any kind will do. See how many slices you can make. Try another mathematical problem of how to get the first slice out without making a mess. This will take much experimentation!
Or eat something round if you don’t like pie. Pizza anyone?? Interesting Books in our library about Pi or π:

• How to Bake Pi: An Edible Exploration of the Mathematics of Mathematics (501.1 CHE)
• Raspberry Pi for dummies (004.165 COO)
• Adventures in Raspberry Pi (J 004.1675 PHI, at Bethesda Branch)
• Raspberry Pi for Kids for Dummies (J 004.165 WEN)
• Why Pi? (J 530.8 BAL)

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