Sequence III: levels for justification and transitivity
In this sequence, teachers were asked to consider multiple ways that students justify the
equivalence of equal-sized parts resulting from equipartitioning. The goal of this sequence
was to formalize the various justification strategies described by the EPLT and introduce
teachers to the idea of the transitive property of equipartitioning. Again, teachers were
engaged through discussions of video recordings of clinical interviews exhibiting the
various justifications that students use, including the emergent relationship of transitivity.
To further focus on this relationship, teachers explored a replication of a rectangle split into
four parts along its diagonals accomplished by one of the children in the recording4
(Fig. 2). From these discussions, justifications and the transitive property of equipartitioning
were formalized, and teachers then viewed a recording of a classroom
equipartitioning lesson to apply their new understandings. Here, we present evidence from
the exploration task of the sequence to further elaborate the selected teachers’ uses of their
SMK to participate in discussions around the professional learning tasks.