Abstract

In this report, the focus is on 10‒13-year old Finnish and Indonesian students’ proportional reasoning skills in a task, which requires an understanding of equality between two ratios. Ideally, every mathematic lesson, even at the primary school level, should develop students’ skills in communicating their ideas by using ‘mathematical language’. Explaining one’s thinking is not easy: for example, 71\% of Finnish students were not able to describe in the test item, how they ended up in their answer, whether it was correct or incorrect. On the other hand, 34\% of Indonesian students left their explanations out. In addition to cognitive elements, social and cultural factors play an important role in student’s performance and strategies.