As we noted, the knowledge that pre-service primary and secondary school teachers
have of negative numbers has not been the subject of much research. Widjaja, Stacey,
and Stente [11] studied number line representations of negative decimals used by 94
pre-service primary school teachers. The authors note that understanding the ordering
of negative decimals and placing them on a number line are a challenging topic for a
significant proportion of the pre-service teachers. Steiner [4] conducted a study with preservice
elementary teachers on how their conceptual understanding of integer addition and
subtraction understanding is impacted by the use of a novel teaching model that combines
the features of the number line model with those of the equilibrium model. This study
showed that the equilibrium model aided the participants’ understanding of the algorithms
for addition and subtraction of integers.