Join the Cat in the Hat as he explains how to measure circles and calculate pi in this perfect choice for Pi Day celebrations and nurturing a love of math and numbers! The Cat in the Hat makes calculating pi—one of the most fascinating numbers in mathematics—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. Fans of the hit PBS show The Cat in the Hat Knows a Lot About That! will be delighted at this new addition to the Learning Library series.