The research presented here takes place in the first year of French university with students graduating in economics and management. Our investigations show that these students do not greatly dislike mathematics, even if they often admit that they have difficulties. Moreover, they generally do not have any opinion about the utility of mathematics for economics. We have experimented with a teaching device, designed to change students' relation to mathematics and show them how to use mathematics in order to solve a problem in which mathematics does not appear at first. This situation is used as a paradigm for mathematical modelling. After a presentation of the context, we will present this sequence with a brief analysis. Finally, we will present a didactical analysis using Brousseau's schema (completed by Margolinas) of the vertical structure of the ‘milieu'.