Abstract
The purpose of this article is to analyse, within the framework of the theory of didactical situations in mathematics, a sequence aiming to evaluate and to develop children’s ability to use their knowledge about the comprehension of decimal number system in a first grade class (students aged 6-7 years) in a primary school. The sequence, mainly based on a communication’s game, consists in carrying out conversions of numbers from the symbolic representation to the collection of the corresponding quantity of objects and vice versa. The game allows the children to test validity and suitability of their procedure. Moreover this sequence allows the teacher to evaluate, in situation, the degree of acquisition of the different representations of number in the decimal number system.