In this paper, I shared that my 77 preservice teachers initially had a difficult time
understanding the mathematical basis for the 2-digit multiplication algorithm, by
exploring three different algorithms (one familiar, and two unfamiliar ones). Then, I
reported that when the preservice teachers worked together in groups to explain the
mathematical basis for the algorithms, they did much better than when they responded
individually. Finally, I shared the steps I took to redress the preservice teachers’ lack of
understanding, namely,