Abstract
In the elementary school teaching guide for the Japanese course of study, the units
on population density and speed are indicated as examples of derived units in
mathematics. However, derived units other than area or volume are not taught in
elementary school lessons. The study investigated this with the aim of obtaining
suggestions on instruction methods concerning “size per unit quantity” and “speed,” based
on the units. Primary school teachers participated in this study and their understanding
of the derived units was examined. Three solutions to each problem for (the number in a
group) × (the number of groups) ＝ (the total number) that were presented to the
participants, who were asked to write down the unit of each value in the solution. At the
same time, the participants’ profiles were asked. Results showed that the participants
understood the derived units of speed, such as “km/h” regardless of their years of
experience as a teacher, and their math or science ability. However, their understanding
about the unit of the quantity calculated by multiplication or division for two types of
quantities without the derived units of speed was not enough.
