"Matt, Bibi, and their dog Riley crawled through the tiny opening first. FWUMP! A secret door suddenly closed behind them . . ."
The Zills family is summoned to Egypt to help find the hidden burial chamber of an ancient pharaoh. But when Matt and Bibi get trapped in the pharaoh's pyramid, they stumble upon an even bigger mystery. With only each other, their dog Riley, and the geometric hieroglyphics on the walls to help them, the twins must use their math skills to locate the burial chamber--and the way out. Luckily, Matt and Bibi know their stuff when it comes to geometric solids, and so will the readers of this adventure in math!

When young Per visits her uncle Sir Cumference and his family, she learns how to play the game, "Inners and Edges." After she finds a clue linking the game to the mysterious castle on the island of Immeter, she must figure out how to find the perimeter and area of a circle to unlock the island's secret.
Math skills taught include finding the area and perimeter of a rectangle and a circle. Introduces an underlying concept of calculus -- using straight lines to measure curves.

Radius is on a quest to earn his knighthood! With only a circular medallion, a mysterious poem, and his own wits to guide him, he must find and rescue a missing king. Includes plastic protractor

Assisted by his knight, Sir Cumference, and using ideas offered by his wife and son, King Arthur finds the perfect shape for his table.

Sir Cumference, Radius, and Sir Vertex search for Edgecalibur, the sword that King Arthur has hidden in a geometric solid.

The eighth book in the popular Sir Cumference series, SIR CUMFERENCE AND THE OFF-THE-CHARTS DESSERT introduces readers to different methods of collecting data.
Sir Cumference and Lady Di of Ameter are in a pickle. The castle cook is sick and the Harvest Faire is coming up--who will make the special dessert for this annual event? Two bakers in town, Pia of Chartres and Bart Graf, are up to the task. But after sampling Pia's delicious pies and Bart's scrumptious cookies, Sir Cumference and Lady Di just can't choose They come up with a solution: hold a contest and let the townspeople choose the dessert to be served at the faire.
When Pia and Bart's methods of tracking their votes fail, they each realize they need to come up with a better system. Pia places a colored candy around the edges of a pie dough and Bart stacks his cookie molds--each color candy or mold shape represents a different kind of pie or cookie. Thus, the pie chart and bar graph are born But when the contest ends in a tie, Pia and Bart concoct a hybrid recipe that everyone enjoys.

A clever introduction to place value.
Sir Cumference and Lady Di planned a surprise birthday party for King Arthur, but they didn't expect so many guests to show up. How many lunches will they need? And with more guests arriving by the minute, what about dinner? Sir Cumference and Lady Di have to figure out a quick way to count the guests to bring order to the party.
Sir Cumference and his friends have been entertaining young and old alike for years as they introduce important math concepts with clarity and humor.

When Sir Cumference drinks a potion which turns him into a dragon, his son Radius searches for the magic number known as pi which will restore him to his former shape.

While riding through the forests of Angleland, cousins Per and Radius realize they are lost and are desperate for a map to guide them home. Soon they come across a mysterious house in the hills. Inside they find a map to a treasure belonging to Xaxon Yellowbearyd, the fiercest Viking warrior of his time. Per and Radius must decode the strange numbered grid on the map, while trying to steer clear of the pack of bungling bandits who are on their tail. Will they find the treasure in time?