In our efforts to reform mathematics education, we've learned a tremendous amount about young students' strategies and the ways they construct knowledge, without fully understanding how to support such development over time. The Dutch do. So, funded by the National Science Foundation and ExxonMobil, Mathematics in the City was begun, a collaborative inservice project that pooled the best thinking from both countries. In "Young Mathematicians at Work," Catherine Fosnot and Maarten Dolk reveal what they learned after several years of intensive study in numerous urban classrooms. In this third volume in a series of three, Fosnot and Dolk focus on how children in grades 5-8 construct their knowledge of fractions, decimals, and percents. Their book: describes and illustrates what it means to do and learn mathematics. contrasts word problems with true problematic situations which support and enhance investigation and inquiry. provides strategies to help teachers turn their classrooms into math workshops. explores the cultural and historical development of fractions, decimals, and their equivalents and the ways in which children develop similar ideas and strategies. defines and gives examples of modeling, noting the importance of context. discusses calculation using number sense and the role of algorithms in computation instruction. describes how to strengthen performance and portfolio assessment. focuses on teachers as learners by encouraging them to see themselves as mathematicians.