This paper is about the representations young students use when they are working on a problem-solving task on combinatorics. Results from previous studies on young students and combinatorics have shown connections between the representations used and the extent to which students solved the task. Based on these previous results, young students in this study were interviewed about their choice of representation. In this paper, the rationales expressed by the students are connected to the representation and stage of systematization shown in their documentation. The results indicate that difficulties in representing the context of the problem-solving task may force some of the students to work with a representation on a level of abstraction not suitable for them. Working with representations at an unsuitable level of abstraction may in turn influence how the students manage to complete the problem-solving task.