Problemi o contesti ricchi e aperti alla matematizzazione?

This article presents a study concerns the understanding of some aspects of the multiplicative structure of decimal numbers. It involved a series of classroom activities in primary school, using “rich context” as starting points for progressive mathematization. To create a substantially modified teaching-learning environment, procedures such as estimation and approximation processes are also introduced. During the teaching experiment, we also laid the basis for overcoming some conceptual obstacles in the development of understanding of the multiplicative structure of decimal numbers. In particular, we addressed the misconception that multiplication always produces a larger result than the factors, an overgeneralization of a rule valid for integers.