Description Sangwigwon Yeonsan 960 approaches number and computation learning—the starting point of math and an essential tool across all areas—with a new philosophy and methodology. Through task-solving computation problems combined with diverse situations, processes, and approaches, this series not only perfects computation skills but also builds higher-level mathematical thinking. Sangwigwon Yeonsan 960 will be a great support for children who get bored or tired of simple repetitive computation drills, children who need creative-thinking computation practice beyond basic arithmetic, children aiming for advanced application of school curriculum, children who need to think through math rather than mechanically solve problems, children who want to build a solid foundation rather than rush into excessive advanced study, children preparing step by step from an early grade for gifted education programs, olympiads, or specialized middle/high schools, and indeed any child who loves math and wants to excel at it. [Book Composition] 6 books for Level P, 4 books each for Levels A–D, 22 books in total D1: 961–1020 Multiplication and Division D2: 1021–1080 Mixed Calculations D3: 1081–1140 Addition and Subtraction of Fractions D4: 1141–1200 Addition and Subtraction of Decimals [Recommended Grade] An essential thinking-skills computation workbook for advanced elementary 4th grade students Table of Contents D3 1081–1140 Addition and Subtraction of Fractions Issue 1: Understanding fractions, proper fractions, improper fractions, and mixed numbers Issue 2: Converting to improper fractions and mixed numbers, comparing sizes of equivalent fractions Issue 3: Addition and Subtraction of Fractions (1) Issue 4: Addition and Subtraction of Fractions (2) Answer Key Included