Fractions, student difficulties in learning fractions, different meanings of fractions, fraction models, equivalence, comparison, sorting, operations with fractions, decimal fractions, operations with decimal fractions, geometry, development of geometric thinking in children, subjects of 2 and 3 dimensional geometry and their teaching, measurement and measurements , development of the idea of measurement in children, size, area, volume, time measurements, weighing, money, data management, tables and graphs, measurement and evaluation in mathematics education, multiple measurement-evaluation methods and techniques, related subjects in the primary school mathematics curriculum, gains and examples of appropriate activity. Fractions, student difficulties in learning fractions, different meanings of fractions, fraction models, equivalence, comparison, sorting, operations with fractions, decimal fractions, operations with decimal fractions, geometry, development of geometric thinking in children, subjects of 2 and 3 dimensional geometry and their teaching, measurement and measurements , development of the idea of measurement in children, size, area, volume, time measurements, weighing, money, data management, tables and graphs, measurement and evaluation in mathematics education, multiple measurement-evaluation methods and techniques, related subjects in the primary school mathematics curriculum, gains and examples of appropriate activity.