Abstract
Many students confuse area and perimeter and are additive in their thinking of area. This
misconception affects their ability to successfully complete area estimation and calculation
tasks. In this paper, a simple pen-and-paper test based on Kidman’s (1999) research into
area judgement rules is developed and trialed and used to detect additive (and
multiplicative) thinking of area estimation. It found that approximately one half of the
students’ intuitively judged area additively showing the power and persistence of this form
of thinking.
Gillian Kidman