The present study describes the usage of strategies of symbolic representation during teaching introduction of decimal system in primary school in Mexico. Our research is based on Activity Theory conception of teaching-learning process and of gradual introduction of scientific concepts in school age. The method includes symbolic external representation of mathematic, logic and spatial relations. Children from the second grade of primary school took part in the study. The children were included

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... n joined actions with constant orientation of the teacher. Specific Program was designed for introduction of decimal system and applied during 6 month 3 times per weak. The results showed that children acquired significant symbolic abilities necessary for understanding the concept of decimal system. We consider that proposed method could be a new approximation for solution of common difficulties which arise at primary school during initial teaching of mathematics.