This math chapter workbook on "Mental Math Strategies" focuses on developing foundational arithmetic skills that promote mental calculation. Key topics include strategies for quick addition and subtraction within 20, such as making ten (using combinations that add up to 10), doubles and near doubles (e.g., knowing 5 + 5 and using it to solve 5 + 6), and counting on (starting with a number and counting up). Number bonds and the concept of "part-part-whole" help students decompose numbers effectively.