Have you ever thought about pi on BART? Not the lemon meringue or deep-dish apple kind — the mathematical one. Turns out pi is used in lots of ways at BART.
Pi is a mathemathical constant, the ratio of the circumference of a circle to its diameter. It's typically written as 3.14159 and is celebrated with Pi Day on March 14.
This year is being called a "once in a lifetime" Pi Day. If you extend the digits out to the hour, minute and second, you get 3.14.15 (March 14, 2015) at 9:26:53 (just before 9:30 in the morning and evening). If you happen to be on a BART train at that time, give a cheer for pi!
You can download a PDF of all the pi examples, and some quizzes inside, to enlarge or print if you want to challenge the math lovers in your home.
