Translation (1994) [EDITED March 2023] of Leerstofrduksie in die wiskundeles (1973). Johanneburg: McGraw-Hill. Chapter 2 edited 4 November 2012. TABLE OF CONTENTS CHAPTER 1: GENERAL AND PARTICULAR PROBLEMS IN TEACHING MATHEMATICS 1.1 Introduction 1.2 General problems 1.3 Specific problems 1.4 Summary CHAPTER 2: THEORETICAL PENETRATION OF THE CONCEPT "REDUCTION OF LEARNING MATERIAL" 2.1 Introduction 2.2 What is learning material? 2.3 The choice of learning material 2.4 What is reduction? 2.5 The phenomenological method 2.6 Husserl and the concept "reduction" 2.7 Summary of Husserl's pronouncements 2.8 Pronouncements of Martin Heidegger 2.9 Summary 2.10 The steps of the reduction as proposed by Spiegelberg 2.11 The didactic category "reduction" 2.12 Reduction of learning material in general CHAPTER 3: THE PLACE AND MEANING OF REDUCING THE LEARNING MATERIAL IN THE LESSON STRUCTURE 3.1 Introduction 3.2 The teaching aim and reducing the learning material 3.3 The course of the lesson and reducing the learning material 3.4 Summary CHAPTER 4: PRACTICAL EXAMPLES TO ILLUSTRATE THE SENSE AND MEANING OF REDUCING THE LEARNING MATERIAL FOR CONSTRUCTING A MATHEMATICS LESSON STRUCTURE 4.1 Introduction 4.2 An example for each phase of the lesson structure 4.3 An example of a complete lesson structure BIBLIOGRAPHY