This mathematics textbook, written in Portuguese, is the third book of a Mathematics Program in Portuguese. It is designed for third graders. It closely follows the objectives and methodology of the major curricula used throughout the schools in the United States. The 11 chapters deal with: numeration (0-999,999); addition with and without regrouping; subtraction with and without borrowing; commutative and associative properties, length, time, weight, capacity and temperature measurements; money; geometric figures, perimeter and graphs; fractions; multiplication, and division and word problems. For each chapter there are objectives, an introduction, activities, sample exercises, practice exercises, a review, and an evaluation. (RH)