In the middle years of school, it is important that mathematics is challenging, engaging and focuses on worthwhile mathematics. In this article, Anne Roche describes a lesson that seemed to have all three of these characteristics, as students grappled with issues of scale to create a fun run, given a range of challenging mathematical constraints. The task was inspired by research on problem solving and the use of contextual tasks that help motivate and engage students with important mathematics. Herein Roche outlines the mathematical focus of the lesson "Sandy Point Fun Run," describes how the lesson played out in some Year 5/6 classrooms, discusses the particular challenges in this task for the students, and highlights its potential for learning a range of important ideas and skills.