This exuberant picture book by Katherine Hannigan, the acclaimed and bestselling author of Ida B, is about math concepts, friendship, and imaginative play, and is told entirely in equations A young girl and her dog spend the day playing in her backyard, where with her imagination--and a few helpful props--anything can happen. What do you get when you combine dirt and water? Mud What do you get when you take a sheet, a flowerpot, and a stick...