Understanding the Concept of Conservation of Area: Recomposing a Shape Will Preserve Its Area

In order to figure out how the students understand the concept of conservation of area focusing on recomposing shapes, this study has designed an instructional learning activities for the third grade students of Elementary school in Surabaya. The study conducted before the students learned the concept of area measurement, even without introducing the concept of area directly. Two different classes were taken to involve in the first cycle and second cycle respectively. This study used design research as the methods and Indonesian version of Realistic Mathematics Education, called PMRI (Pendidikan Matematika Realistik Indonesia) as an approach to support the learning process of conservation of area. Real life context based on five tenets in PMRI which is making table-cloth from the cloth-rag and the shape of rice field was chosen in developing a sequence of learning activities to reach the learning goal. In the implementation of learning activities such as making table cloth and comparing rice field could be used to reveal the idea of recomposing in the concept of conservation of area. From those activities, the students build their understanding that recomposing preserve the area of a shape because none of the parts of the shape are wasted or leftover (identity concept). They also found that two shapes can have the same area although they have different form. Somehow, some students were found still struggle with the way to recompose a shape. They showed that it was difficult to figure out which parts of the shape to be cut and where to be placed. Keywords: the concept of conservation of area, recomposing a shape