Promoting argumentation as a socially situated practice through informal mathematical project

he paper presents a retrospective analysis of La Tombola Infernale, a project situated within Informal Mathematics Education and grounded in the Design-Based Research methodological framework. The project engages students in designing and playing a Dante-inspired tombola game, through which they explore both mathematical concepts and the Inferno canticle of the Divine Comedy. Drawing on Ferrari and Saccoletto’s (2023) theoretical perspective on argumentation as a socially situated practice, the study investigates how this specific informal learning context supports the development of students’ argumentative processes. The analysis focuses on one design cycle— implemented across different age groups and settings—highlighting the role of peer interaction, linguistic resources, and material artefacts in fostering collective meaning-making and the progressive formalisation of modular arithmetic.