At the end of primary school all children more of less know what a percentage is, but yet they often struggle with percentage problems. This article describes a study in which students of 13 and 14 years old were given a written test with percentage problems and a week later were interviewed about the way they solved some of these problems. In a…

This study used a diagnostic testing approach to compare the mathematics achievement of eighth-grade students across a sample of 20 countries, analyzing data from the Third International Math and Science Study-Revised (TIMSS-R, 1999). Using the rule-space method, student mastery was measured on 23 specific content knowledge and processing…