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 and make a costume? You transform yourself into Her Majesty, the queen! A cape and a strong breeze turn the treehouse into an airplane. A sheet, a stick, and a pair of well-placed cat's ears turn the girl into a pirate! At least until mutiny leaves her alone in her kiddie pool . . . surrounded by sharks! Cheerful and action-packed illustrations and a combination of comic-like panels, conversation bubbles, sound effects, and full-page illustrations make Dirt + Water = Mud particularly appealing for new readers.