The seven ducklings in the books split into all the whole number combinations that make seven. First children count all seven ducks, then the ducks slide, hide, chase, splash, and quack in the combinations 6 + 1; 5 + 2; 4 + 3; 3 + 4; 2 + 5; 1 + 6, and finally all seven fly. This book helps children understand that numbers are composed of smaller numbers. This is the same mathematical idea in the How Many Are Hiding gameâ€”numbers are composed of parts that make up the whole.