Creating number concept up to 100

This diploma thesis deals with third-graders from one of Prague's elementary schools and their understanding of numbers. In addition to the Prodos textbooks, some didactical ideas were taken from the Fraus textbooks, which are aimed at the development of children's understanding mathematics. The experiments were carried out in a classroom and lasted one and a half year. Seven pupils were chosen to take part. The experiments were aimed at gauging their semantic and structural understanding of numbers. The pupils worked individually and were individually interviewed after the experiments. The assumption that pupils use strategies that are not taught in the classroom was confirmed, as well as the fact that the operation of subtraction is much more complicated than addition in mental arithmetic and also in written counting. However, the assumption that the pupils perform better when faced with financial matters as opposed to other situations was not confirmed. It came to light that when creating a verbal task, it is necessary to consider the pupil's understanding of the vocabulary used. Key Words: addition, subtraction, decomposition of number, computation, mathematics, calculative strategie