The 26 activities described in this volume deal with a wide variety of mathematical ideas. Most of the activities are appropriate for grades 6-9; many could be used with older or younger groups as well. All activities are described in detail; some descriptions include sample worksheets, and several provide suggestions for followup activities. The topics include magic squares, unit fractions, number of relations, Pythagorean triples, a physical model (braiding) for teaching group structure, flexatubes, puzzles, use of the minicalculator, exponents, approximating the value of pi, the metric system, probability and statistics, mathematics vocabulary, sports in outer space, measuring in space, and mathematics of music. The activities vary in approach and purpose; several are discovery oriented, while others are designed for reinforcement. Some of the activities are designed to encourage students to think beyond their initial reactions to find unexpected methods to solve problems. (SD)