PRODUCED AS PART OF A PROJECT FOR THE IMPROVEMENT OF CLASSROOM TEACHING, THIS BOOK DISCUSSES THE BASIC CONCEPTS AND OPERATIONS OF ARITHMETIC WHICH ARE TAUGHT TO ELEMENTARY SCHOOL STUDENTS. THE CONCEPT OF A SET IS USED THROUGHOUT AS A BASIS FOR EXPLANATION, AND THE DISCUSSION STRESSES WAYS BY WHICH STUDENTS CAN BE BROUGHT TO UNDERSTAND THE CONCEPTS. THE FIRST CHAPTER COVERS BEGINNING NUMBER CONCEPTS--SETS, PAIRING, COUNTING. SUCCEEDING CHAPTERS COVER THE DECIMAL NUMERATION SYSTEM, ADDITION, MULTIPLICATION, SUBTRACTION, DIVISION, ALGORITHMS FOR ARITHMETIC COMPUTATIONS, AND THE WHOLE NUMBER SYSTEM. THE FINAL SECTIONS OF THE BOOK INCLUDE ANSWERS TO THE EXERCISES GIVEN IN THE CHAPTERS AND DESCRIPTIVE DEFINITIONS OF TERMS USED. THIS DOCUMENT IS AVAILABLE FROM THE NATIONAL COUNCIL OF TEACHERS OF MATHEMATICS, 1201 SIXTEENTH STREET, N.W., WASHINGTON, D.C. 20036. (DR)