Sir Cumference is a series of children's educational books about math by Cindy Neuschwander and Wayne Geehan.
The books have been studied for their use in mathematics education.[1]
Most of the characters of the book are named after math terms, such as Sir Cumference (circumference).
Sir Cumference is a knight in the kingdom of Camelot. He has a wife called Lady Di of Ameter and a son named Radius.
Di of Ameter is the wife of Sir Cumference. In the first book, she came up with all the different shapes of the table (parallelogram, square, etc.) and in Sir Cumference and the Dragon of Pi, she stayed with Sir Cumference when he turned into a dragon.
Radius is the son of Di of Ameter and Sir Cumference. He has a friend named Vertex in Sir Cumference and the Sword in the Cone, and plays an important role in both Sir Cumference and the Dragon of Pi and The Sword in the Cone first by turning his father to a dragon and back, and later assisting Vertex in becoming King. He is the focus of Sir Cumference and the Great Knight of Angleland, in which he becomes a knight after rescuing King Lell and his pair of dragons.
Vertex is the best friend of Radius. He appears on the first page of Sir Cumference and the Sword in the Cone. He is quoted saying, "I've found out why King Arthur called us all here!" Sir Cumference and Radius agree Vertex should be the heir to the throne.
Currently, there are 11 books in the series: