The Support of Big Ideas toward Mathematical Strategies

A. Introduction
Addition and subtraction problems potentially create many strategies for children to solve. The strategies which can be used are, for example, adding on or counting up, counting back, splitting, removing, taking away, etc. The use of strategy by students depends on the numbers which are available in contexts or questions. Moreover, it is mainly influenced by the understanding of students toward the mathematical idea behind the contexts. When talking about contexts of subtraction, there are mostly three kinds of them which often appear in classroom: subtraction in the form of distance or difference, removal, and comparison. The three kinds of them are categorized as mathematical ideas that students are expected to grasp. In this report I will make report and use the examples in the video Addition and Subtraction Minilessons, Grade pre-3. In the video, Michael Galland, as a teacher and his students are involved in discussion of addition and subtraction problems. The students use many different strategies of some problems which are given by Michael.