Sir Cumference and the Viking's Map

In Sir Cumference and the Viking's Map (Charlesbridge Math Adventures (Paperback))Cindy Neuschwander continues her Sir Cumference series with an exploration of coordinate geometry.

Radius and Per discover Viking Xaxon Yellowbearyd's map with axes (yes a play on the word axis) and must learn how to read the gridded map. It appears maps are not common in Angleland. The children learn through trial and error that the X is read before the Y and decide that it is because X comes before Y in the alphabet. The children are chased by robbers who want to capture the treasure and helped by the ghost of Xaxon Yellowbearyd himself. Children may be surprised by the treasure, but it ties to the skills Per and Radius have acquired from their journey and more valuable to the kingdom than gold.