ACKNOWLEDGEMENTS CHINESE ABSTRACT ABSTRACT CHAPTER I INTRODUCTION Background Statement of the Problem Theoretical Framework Research Questions Definitions of Key Terms Limitations of the Study CHAPTER H REVIEW OF THE LITERATURE Aiming at a Conceptual Understanding of Fractions, Decimals and Percents External Representations and Internal Representations The Role of Different Forms of External Representations in Developing Conceptual Understanding of Fractions, Decimals and Percents Relationship between Different Forms of Representation and Achievements The Role of the Textbooks in Facilitating Learning Fractions, Decimals and Percents Impact of Instructional Time and Teaching Quality on Student Achievements Theoretical Foundations and Rationale CHAPTER III METHODOLOGY CHAPTER IV RESULTS CHAPTER V DISCUSSION AND CONCLUSIONS REFERENCES