The starting point of this article is the question, "how might we inform an epistemology of numeracy from the point of view of better preparing young people for workplace competence?" To inform thinking illustrative data from two projects that researched into mathematics in workplace activity and the teaching and learning of modelling in the classroom is used albeit, by necessity, briefly. Analysis draws attention to the crucial role that understanding the structure of the contextual situation plays in developing a mathematical model of this. It is at this coupling of reality and mathematics that insight into, and understanding of, both mathematics and reality can be developed--or not. This important issue is illustrated with reference to two specific workplace situations that draw on understanding of fraction as gradient and explore how we might use a model of this to scaffold understanding of both reality and mathematics and how each might support the other. With a focus on model formulation during classroom activity attention is then drawn to how students tend to work towards reaching a solution to a particular problem with the consequence that their mathematical representation of the reality does not easily allow for consideration of variation of key factors. In conclusion a research agenda is proposed that seeks to inform an epistemology of numeracy by focussing on numerate activity at the nexus of reality and mathematics by (1) structuring mathematical knowledge using "mathematical" models that might be used to provide insight into a range of models of workplace realities, and (2) requiring student engagement with repeated use of models in ways that emphasise exploration of variability in key factors of the realities that the models represent.