L'apprentissage des nombres décimaux, des nombres rationnels représentés par le système décimal de position

(eng) Decimal fractions are the subset of rational numbers that can be written as common fraction with a power of ten as denominator (e.g., 2/10) or using the place-value system (e.g., 0.2). Learning about decimal fractions is notoriously difficult for children. In a first study, we investigated the impact of prior knowledge and the developmental changes in the comparison of decimal fractions. We distinguished the impact of the value of the digits from the impact of the length of the fractional part on children's pattern of responses. Although both kinds of impact affected the success rate, the digit values had a stronger impact and were mastered later than the length. In a second study, we aim to investigate the age-related changes in rational numbers processing using three notation formats: decimal (e.g., 0.5), decimal fraction (5/10) and fraction (1/2) notations. Results showed that fraction notation of rational numbers is mastered later than the decimal notation. A third study investigated the precursors of decimal fraction processing through a longitudinal study. Results show that the decimal system understanding was the stronger predictor of further performance on decimal fractions. In a fourth study, we investigated the impact of a problem-centered intervention based on the approximation of real numbers in the decimal system. Results indicated that the intervention led to improvement in both conceptual and procedural knowledge. Finally, we investigated the impact of the euro symbol on the processing of decimal fractions. The results showed that the euro symbol stressed the processing of the fractional part of the decimal part of the decimal as a natural number.