The Warlord's Messengers — Virginia Walton Pilegard

The warlord's presence is requested at the emperor's banquet in two weeks, but he is sixteen days away by horseback. Using their math skills, ingenuity, and the wind, Chuan and Jing Jing reach the warlord's camp and encourage him to use their sailing cart to travel to the feast. The Warlord's Messengers is the sixth book in the acclaimed Warlord's Series, and includes directions for making your own windsock as well as suggestions for velocity-related math activities.