Rational numbers are important as a foundation for later mathematics learning and particularly for learning algebra. Most researcher agree that students find rational numbers difficult. This article question the traditional use of partitioning as the starting point for the teaching of fractions. It seeks the origin of childrenâ€™s understanding of rational numbers in their understanding of division. A number of empirical studies are presented on childrenâ€™s use of action schemes for division; correspondence and partitioning. At last conclusions and implications for education are drawn.