The unfolding of an affordance, as an opportunity for action, during a learning activity requires the learner to interact with mediating artifacts. The design of a learning activity involves appropriating affordances and embedding them in the activity in such a manner that the learner is invited to unfold the affordances, through interaction with their mediating artifacts in accordance with pre-defined hypothetical learning trajectories. In this paper, the notion of affordances is used explicitly in the discussion of two previous research efforts. We argue that the notion of affordances, which was tacitly used in these efforts and aligns well with the methodology of scenario-based design,may beused as an instrument for the collaborative design of innovative mathematical learning activities.