This workbook has been newly published to reflect the revised 2022 curriculum, effective from 2024. 1. Ten problems solved with the mind matter more than a hundred solved by hand. Computation practice that only teaches calculation methods can build "calculation skill," but it doesn't necessarily translate into real "math ability." Just as calculations have their own principles and methods, each type of calculation has its own properties and relationships to other calculations. Children also need to be able to apply calculations in practical ways and use them to build number sense. To make this kind of well-rounded, multidimensional computation training possible—rather than teaching calculation as a flat, one-dimensional skill—each concept is explored from multiple angles, with every problem carefully designed based on solid mathematical reasoning. 2. Math that includes real mathematical understanding—not just the four basic operations—builds a strong foundation for elementary, middle, and high school math. Because math is a subject that connects continuously from elementary through middle and high school, the concepts formed in elementary school directly affect learning in later years. Concepts learned in elementary school may seem simple, but they are closely tied to important ideas in middle and high school math, making it essential to learn computation in a way that highlights its true mathematical meaning. This workbook also introduces mathematical principles used in middle and high school in a way that's accessible at the elementary level, helping to anchor a student's overall math learning early on. 3. True understanding comes from thinking, solving, and feeling—not just calculating. Computation practice that involves nothing but repetitive calculation from start to finish can bore children and cause them to miss the mathematical meaning behind the numbers. This workbook creates a multidimensional learning structure that helps children understand the mathematical principle behind each calculation method, connecting computation practice directly to conceptual understanding. The answer key also includes special notes explaining why each math concept matters and how it connects to future learning in middle and high school. Contents: 1. (Two-digit number) + (One-digit number) with carrying 2. (Two-digit number) + (Two-digit number) with one carrying step 3. (Two-digit number) + (Two-digit number) with two carrying steps 4. (Two-digit number) − (One-digit number) with borrowing 5. (Two-digit number) − (Two-digit number) with borrowing 6. Calculations with three numbers (1) 7. Calculations with three numbers (2)