“…The review revealed a gap between students' procedural and conceptual knowledge of fractions Post, Cramer, Behr, Lesh, & Harel, 1993;Prediger, 2008), resulting in a rather instrumental understanding of the procedures Prediger, 2008). Regarding the conceptual understanding of fractions, research pointed at a multifaceted nature of fractions ) and distinguished five sub-constructs to be mastered by students in order to develop a full understanding of fractions Moseley et al, 2007). Related sudies revealed that students were most successful in assignments regarding the part-whole sub-construct, and that in general, they had too less knowledge of the other sub-constructs; especially knowledge regarding the measure subconstruct seemed to be lacking .…”