This book features investigations in each of the five content areas of Principles and Standards for School Mathematics. In addition to using Eratosthenes' sieve to identify prime numbers, fourth graders evaluate algebraic relationships in contracts between theatre owners and movie distributors. They consider geometric possibilities for rectangular puzzles, convert surprising real-world measures into equivalent but more comprehensible measures and examine tables and graphs to extrapolate missing data. As they work, they infer, generalise, reason by analogy, recognise relationships and make representations and they also guess, check and revise and verify their results. The supplemental CD-ROM features interactive electronic activities, master copies of activity pages for students and additional readings for teachers.