Teaching/learning rational numbers, especially fractions, is one of the subjects in which students and educators face difficulties, not only in Greece but also worldwide. The aim of this textbook is to modernize the teaching of fractions and decimal numbers in primary school. A modern teaching method is proposed from the 1st to the 5th grade of primary school for fractions and decimal numbers.

This book includes a verticalization and transition from the theory of teaching rational numbers to teaching practice and vice versa. There is a first theoretical part that scientifically analyzes the difficulties in teaching and learning fractions and decimal numbers, as well as all the factors that affect modern teaching, such as representations, number line, estimations, technology, etc.

Then, a modern curriculum for teaching fractions and decimal numbers in primary school is proposed and analyzed. Finally, based on this curriculum, educational material is presented, such as a teacher's book, a student's book, and a workbook for teaching fractions and decimal numbers from the 1st to the 5th grade of primary school.