As the Arithmechicks slide down the slide, swing on the swings, and play hide-and-seek, they don't realize that a lonely mouse is copying them, longing to join in. However, when their basketball becomes stuck, the chicks discover that a two-inch-tall new friend is exactly what they need. In this heartwarming story, there are many ways to add up ten cheerful chicks--but a new friend is what makes them cheer.