Analysis of models used by student primary teachers when addressing a geometric estimation task

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We present a qualitative research study aimed at exploring the models produced by student primary teachers when addressing an estimation task in which the three spatial dimensions play a major role and the objects whose quantity is to be estimated are deformable. Under a grounded theory approach, we analyse the written productions of 80 student primary teachers who were asked to quantify the amount of bunches of grapes that fit in a box of given dimensions. We highlight the diversity of models (linearisation, base unit, density, direct estimate, counting; also found in studies with other kind of tasks) and of quantities (volume, length, area, weight) on which their modelswere based. Geometric considerations (e. g., using a geometric body to model a bunch of grapes) were mainly in the service of metric interests (calculating volumes) and rarely to spatial ones (arranging bunches). Our findings extend and add value to those observed in related studies.