Lady Di and Sir Cumference know just how to cheer up their gloomy king: with a surprise birthday party! But things get a little out of control when partygoers fill the castle from tower to moat. Now, the only way to pull things together is to organize the crowd — but how? As Lady Di and Sir Cumference discover that the simplest way to get things under control is to group the guests into tens, hundreds, and ultimately thousands, students can see the concept of place value acted out with their own eyes! The "Sir Cumference" math series uses the power of reading (and humor) to enhance students' understanding of math concepts. As Sir Cumference, Lady Di of Ameter, and their son, Radius, come up with clever solutions to Camelot's problems, readers will find themselves understanding concepts of geometry and fractions with ease.