Abstract
The study is part of design research on the teaching of combinatorics. Its main focus is the students’ use of isomorphism when solving combinatorial problems before and after the intervention.
The data come from a pilot intervention in one secondary school class and consist of students’ written solutions to problems and interviews with selected students. We have distinguished three qualitatively different strategies based on isomorphism: re-coding, solving an isomorphic combinatorial problem and solving an isomorphic problem from a different area of mathematics.
These strategies are illustrated by students ’ solutions and excerpts from the interviews. There was an increase in the use of the strategies based on isomorphism after the intervention, but it remained relatively low.
After a time delay, the number of such strategies decreased. Possible implications for the new rounds of intervention are discussed.