This textbook has been published to reflect the newly revised 2022 curriculum, which takes effect starting in 2024. 1. Ten problems solved with the mind matter more for math skills than a hundred problems solved by hand. Calculation practice that only focuses on learning methods can build "calculation ability," but it does not necessarily lead to true "math skills." Just as calculation has principles and methods, each type of calculation has its own characteristics, and there are relationships between different calculations. Children also need to be able to apply calculations and develop number sense through them. To make this kind of well-rounded, multi-dimensional calculation training possible—rather than just one-dimensional practice—this book is designed with problems that allow children to think about a single calculation from various angles, based on solid mathematical reasoning. 2. Only calculation practice that contains real mathematical meaning—not mere arithmetic—can solidify math skills from elementary through high school. Because math is a connected subject spanning elementary, middle, and high school, the concepts formed in elementary school affect learning in later years. Concepts learned in elementary school may seem simple, but they are connected to important concepts in middle and high school, making it essential to learn calculation in a way that highlights its mathematical meaning. This book also allows children to experience, from an elementary level, the mathematical rules they will encounter in middle and high school, helping to anchor their overall math learning. 3. Thinking, solving, and feeling are what make math concepts stick. Calculation practice that focuses solely on computation from beginning to end can bore children and cause them to miss the mathematical meaning behind the calculations. This book creates a multi-dimensional learning structure that helps children understand which mathematical principles underlie each method of calculation, connecting calculation practice to genuine conceptual understanding. In addition, the answer section separately explains why the math concepts in each problem are important and how they connect to middle and high school learning. Contents: 1. Multiplication of Fractions and Whole Numbers 2. Multiplication of Unit Fractions 3. Multiplication of Proper and Improper Fractions 4. Multiplication of Mixed Numbers 5. Fractions and Decimals 6. Multiplication of Decimals and Whole Numbers 7. Multiplication of Decimals