The Double-Decker Bus: Early Addition and Subtraction (Contexts for Learning Mathematics, Grade K-3: Investigating Number Sense, Addition, and Subtraction)

"Contexts for Learning Mathematics" series is designed to support a conceptual understanding of essential mathematical ideas, strategies and models. Each unit provides a two-week sequence of investigation, minilessons, games, and other contexts for learning. The series' 18 classroom-tested units are organized into grade-appropriate levels.