Entrance to Negative Number via Two Didactical Environments

Abstract Early number sense is built within child's everyday life experience. A number is represented as a state (5 apples), address (5th floor), operator of comparison (Mike is 2 cm taller than Tom) and operator of change (I lost 5 Euros). This study presents didactical environments that enable young pupils to gain ample experience with a number as an operator that opens the doors to the understanding negative numbers. In the paper we describe how pupils gain experience with operators through the didactical environments of Stepping and Staircase. Such experience further enhances their effectiveness in solving of dynamic word problems.