Description: Top-Tier Calculation 960 approaches number and arithmetic learning—the starting point of math and an essential tool across all areas—with a new philosophy and methodology. Through problem-solving-based arithmetic questions combined with diverse situations, processes, and methods, this workbook not only completes arithmetic skills but also builds higher-level mathematical thinking. Table of Contents C1 721~780: Addition and Subtraction of Three- and Four-Digit Numbers Issue 1: Addition and Subtraction of Three-Digit Numbers (1) Issue 2: Addition and Subtraction of Three-Digit Numbers (2) Issue 3: Addition and Subtraction of Four-Digit Numbers (1) Issue 4: Addition and Subtraction of Four-Digit Numbers (2) Answer Key