EN
Focusing not only on procedural skills, but also on conceptual understanding, is a very important aspect of teaching mathematics. One possible way to promote students’ understanding is to use problem solving in the classroom. The two key elements of designing a problemsolving activity are selection of the task and organization of the instructions. In this article, a new category of tasks, named Student-Friendly Tasks, is characterized, and a way to use these tasks in the classroom is proposed. One task fitting this category has been chosen, and the process of solving it, by a group of students and by individuals, is analysed in detail. The claim is that this proposal can serve as a didactic tool to engage students in mathematical reasoning and help them develop a deep understanding of mathematics.