This booklet is the print component of a Title II-funded package designed to enhance elementary school mathematics instruction through a problem solving approach that promotes mathematics learning in an environment of inquiry, risk taking, and classroom dialogue. The other component is a 28-minute videotape in which teachers present each of the three lessons described in the booklet in actual classroom settings. Lessons include the use of physical models for representing concepts, and each lesson also involves students working in whole-group and small-group settings. Each lesson includes the objective, lesson summary, materials, warm-up, development of the lesson, assessment, extensions, and follow-up activities. The lessons are also characterized by student involvement and teacher questioning. The project lessons cover the topics of probability for level K-2, money and problem solving for level 2-4, and comparing fractions for level 4-5. (KR)