DEVELOPMENT OF MATHEMATICAL COMPETENCIES WITH MANIPULATIVE GAMES - For children of 6 to 12 years - Manipulation is a necessary and indispens able step for the acquisition of mathematical competencies. But it is not manipulation which is the most important, but the mental effort th at this stimulates when children have the possibility of having differ ent materials in their hands and use games as a learning resource. Onl y after a working with manipulative games are they able to progressive ly use more elaborate resources of mathematical representation as virt ual simulation or pencil and paper work.