Conocimiento especializado de los estudiantes para profesor de primaria en la resolución de problemas de proporcionalidad compuesta basada en las unidades de medida

Considering the importance of proportional reasoning in the mathematical training, and taking into account papers that show the difficulties generated by the development of this knowledge, we try to identify the specialised knowledge movilised in the resolution of a compound proportion problem of four prospective primary teachers. Using the Mathematics Teachers’ Specialised Knowledge model (MTSK) we analyse the resolution methods used, detecting evidences and traces of such knowledge, as well as the opportunities that allow us to identify the knowledge evoked by the answers. The results show a richer knowledge when using resolutions based on the magnitude measure units.