March 14 is Pi Day, an annual celebration of the mathematical constant of pi, representing the ratio of a circle's circumference to its diameter. The holiday is observed on March 14 or 3/14 because 3.14 are the first three digits of the infinite number pi — 3.14159 ... and on and on.

The man last known to be seen with a University of Pittsburgh student before she vanished from a beach in the Dominican Republic gave more details to local prosecutors about the last time he saw her,

From schoolkids learning about constant numbers to pizza deals to school serious math equations, here’s a slice of Pi Day fun.