In this master thesis, we investigated which misconceptions about fractions occur in 5th grade students and how the use of different models affects their understanding.
The theoretical part presents key aspects of the concept of fractions, common misconceptions of students and the importance of using different visual models in teaching. Particular emphasis is given to surface, length and set models and their influence on the formation of conceptual understanding of fractions.
The survey was based on a diagnostic test and semi-structured interviews, and the data were analysed using descriptive statistics and content analysis. The aim of the study was to find out how the choice of model type (surface, length, set model) affects the understanding of different aspects of the fraction concept and the elimination of misconceptions, as well as how students justify their strategies and explain their mistakes when solving fraction problems. We were interested in whether Grade 5 pupils have difficulties in understanding the meaning of numerator and denominator, in identifying equivalent fractions, in identifying and representing fractions greater than or equal to 1, and in recognising the analogy between the two versions of the length model - the number strip and the rectangular strip. We also tested the role of overgeneralisation in transferring rules that apply to the set of natural numbers to the set of rational numbers.
The findings show that Grade 5 pupils often have difficulty understanding the meaning of numerators and denominators and identifying equivalent fractions. When comparing and ordering fractions, they often transpose rules from the set of natural numbers (e.g. inferring that a larger denominator means a larger fraction) and focus on counting parts rather than the relationship between the part and the whole in models. The results confirm that visual models can significantly support understanding, but their performance is not equal (e.g. length models help to compare the size of fractions, whereas set models often reinforce misconceptions in this case). The findings will contribute to more effective teaching of fractions and to the design of didactical approaches tailored to students' understanding. The changes foreseen in the new curriculum further substantiate the relevance of the topic.
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