This is a book created to reinforce the idea of subtracting by 1 or "one less". The book begins with ten ducklings in a pond and one by one they leave the pond. The students must read the number words within the word problem and complete the number sentence. The illustrations also show the number of ducks in the pond and decrease with each page. When copied back-to-back there is one blank page left. This page can be used for students to create their own word problem with a number sentence and illustration.