This resource serves as a comprehensive teacher's guide on the 'Doubles Plus 1' strategy, a mental math technique aimed at enhancing students' addition skills, particularly for consecutive numbers. The guide outlines the concept's overview, teaching strategies, and creative classroom activities such as the 'Mirror-Mirror' game and 'Neighbor Search.' It emphasizes the importance of mastering basic doubles, visualizing relationships with tools like Unifix cubes, and engaging students to verbalize their thought processes. The resource also includes various practice sets and exercises aimed at reinforcing the understanding of the 'Doubles Plus 1' concept through systematic practice. Teachers are encouraged to check for understanding and implement a timed fluency assessment to gauge student progress and mastery.