Textbooks are frequently used as a resource to teach children how to solve word problems in mathematics classes. The solving models explicitly proposed by textbooks, and the kind of problems they propose, can therefore have a decisive influence on the way in which students learn to solve them. This paper analyses the extent to which the problem solving models proposed by the books include reasoning as one of the steps needed to solve a problem. To do this, the processes and steps articulated in the models proposed in the books by Anaya, SM and Santillana are categorized according to data, reasoning, choice of operation, strategies, execution of operations, expression of results, checking and inventing. The results indicate that reasoning processes are hardly ever found in the models, especially in lower year courses. It is concluded that mathematical textbooks provide incomplete solving models that fail to promote reasoning. [ABSTRACT FROM AUTHOR]