Because of our fascination with this
problem, we decided to pose it in a methods
course for preservice high school teachers in
order to investigate how they attempted to
solve it. We also wanted them to refl ect upon
the implications of allowing their future
students to use or not use manipulatives for
solving problems. Please note these students
were seniors who were earning dual majors
in mathematics and education. Rather than
working individually (as was the case in the
high school classroom which we observed),
the preservice teachers worked in groups of
three. Similar to the enactment in the high
school classroom, we gave the preservice
teachers no manipulatives and posed the
problem. We supplied them with chart paper
and markers and walked around the classroom
in order to listen to their strategies. All groups
of preservice teachers drew cubes on their
chart paper but none of them labeled the
vertices in order to keep track of the triangles
in an organized way. Th ey seemed to move
directly from their sketches of cubes to using
symbolic representations with numerals,
factorials, and ratios.
After about 15 minutes of allowing the
groups to explore the problem, we brought
the class together as a whole group and
asked them to share their thinking about
the problem. Needless to say, during this
conversation they told us they “wanted” and
“needed” concrete manipulatives – cubes and
triangles – in order to be more confi dent about
their strategies. Following this conversation,
we gave the groups cubes (similar to the ones
shown in Figure 1), scissors, and foam board.
For a second time, they explored the problem
in their groups.