The Cat in the Hat makes calculating pi--one of the most fascinating numbers in mathmatics--as easy as pie! Using a piece of string and two sticks, the Cat first shows beginning readers how to draw a perfect circle. Then, using a can and a piece of ribbon, he shows how to measure a circle's circumference and diameter, and to use those measurements to calculate pi. Also included is information about the history of measurement and famous Pi Pioneers! Written in simple rhyme, Happy Pi Day is a natural choice for celebrating Pi Day (held annually on March 14), and for nurturing a child's interest in math.