Cass is a whiz at math, but that's little consolation to this young African-American girl when she wants to learn double Dutch. Her feet can't keep even one rope from getting tangled. Her brothers, Jackson and Bud, write a rhyme to help Cass keep the rhythm when she jumps. When Cass blows the beat of the rhyme on the whistle she won in a school math contest, she learns how to jump a single rope. But will she ever learn double Dutch? To Cass's pleasure and surprise, her math skills play an unexpected role in how she masters the difficult footwork in this satisfying story about a young girl adjusting to life in her new city neighborhood. (Ages 6-8)