Introduction. Children take years to learn symbolic arithmetic. Nevertheless, such as animals and human adults, infants and children can represent approximate number in arrays of objects and sequences of events, and use these capacities to perform approximate addition and subtraction. Objective. To evaluate whether preschool children without formal education could perform non-symbolic additions, through abstract representations. Methods. We evaluated 17 preschoolers from a private kindergarten recruited from the city of Buenos Aires. They had to add to groups of blue dots, and then compare their addition with a third group of red dots, determining if the blue or the red dots were more numerous. We measured accuracy of responses of each child. Results. Across all the problems, children performed well above chance (67.89%, chance=50%, t(16)=6.89, p <0.001), showing the characteristic ratio effect [F(1, 16)=8.45, p <0.01, ANOVA], and without resort to non-arithmetic strategies. Conclusions. This study provides further evidence regarding the non-symbolic arithmetic skill present before formal education, and together with recent research, raises important contributions in education, trying to understand how children learn mathematics and to establish new methods of teaching.