Presented is the third edition of a textbook designed for pre- and inservice teachers of elementary school mathematics. The content was selected on the basis of its direct applicability to the mathematical ideas usually introduced in grades K-6. The content is presented in conjunction with appropriate teaching strategies, determined by research findings and relevant contemporary trends. Each concept presented is followed by related activities for children. Sixteen chapters consider: pre-number concepts; our base-ten numeration system; addition and subtraction; multiplication and division; factors; multiples, primes, and composites; representing, adding, and subtracting rational numbers; multiplying and dividing rational numbers; common mathematical difficulties; problem solving; geometric figures and relationships; children's development of geometric ideas; attributes of measurement; measurement of attributes; organizing, representing, and interpreting data; computer use; and planning and managing instruction. Appendices contain an instructional objectives chart, selected answers for exercises, and material sheets. (MNS)