This report considers the reasoning of sixth grade students as they explore problem tasks concerning the fairness of dice games. The particular focus is the students' interactions, verbal and non-verbal, as they build and justify representations that extend their basic understanding of number combinations in order to model the outcome set of a probabilistic situation. Several models are posed and students discuss and debate their differences and similarities. Analyses of student-to-student and student-to-researcher dialogue reveal an emphasis on sense making and collaboration in the quest for meaning. This resulted in richer and deeper understanding of the conditions of the problem and the varying interpretations developed by the students. (Contains 1 footnote and 1 figure.) [For complete proceedings, see ED500859.]