New to the Fifth Edition *Inspired by one of the five process standards in the NCTM Principles and Standards', Content Connections is a new feature that highlights the connections between content areas in mathematics in various chapters. *NCTM icons appear in nearly every chapter and point explicitly to the alignment of this book with the NCTM Principles and Standards through excerpts and commentary. *Investigations in Number, Data, and Space and Connected Mathematics features spotlight examples of these two popular reform curricula for the K-5 and 6-8 grade levels, respectively. These excerpts occur in every chapter in Section 2, include an activity from the program along with a description of the surrounding content. The purpose is to acquaint students with materials reflecting the spirit of the NCTM Standards and the constructivist philosophy of the book. *Stop and Reflect features indicate places throughout the book to pause and become truly engaged with an idea. *Chapter 6, Planning in a Problem-Based Curriculum- includes a new step-by-step guide for planning student-centered lessons. A distinction between practice and drill provides a new perspective on the issue of drill. *