Research on prospective primary school teachers’ (PPSTs’) understanding of the concept of ratio and its application to everyday life has shown that this can be problematic for many student teachers. As the concept is important in the development of proportional reasoning, which underpins many areas of primary school mathematics, questions arise about the PPSTs’ ability to facilitate its development for the children they teach. The “ATEE Ratio Project,” started in 2011, has contributed to the research, chiefly using an instrument designed to elicit from individual respondents the meanings that they ascribed to ratio, the uses (both their own and other people’s) of ratio that they identified, and the ways in which they represented the concept in particular by symbols and drawings – all measures of understanding. For the present study, the research instrument was utilised differently: as a stimulus to discussion (in “Think, Pair, Share” mode), with the aim of investigating if participants’ understanding could be enhanced by this exercise. The work was undertaken in a Mathematics Education module with Professional Masters in Education students in one institution in Ireland, and focused in particular on usage in everyday life. This paper reports on the study, presenting and discussing the findings with reference to the previous Irish and international work. Initial findings suggest that embedding the concept in everyday life contexts helps facilitate PPSTs’ understanding and application of ratio, and should therefore help in supporting the development of their own students’ understanding of the concept.