Adolescence is a transitional period, where the life patterns of adolescents undergo changes, including ways of behaving, associating, ways of thinking and various other patterns of life that characterize adolescents.Things that become a reference are adolescents who are unable to control themselves so that they lose control and fall into deviant b

The present study deals with initial formation of concept of decimal system in second year of education at primary school in Mexico (City of Puebla).Our research is based on Activity Theory conception of teaching-learning process and of gradual introduction of scientific concepts in school age.The method has been designed and worked out with the he