In this paper a two-stage research study is described focused on problem solving relevant to place-value and on the use of the operations within the calculator environment. The findings show that in this specific environment and via appropriate tasks teachers are provided with a context to better understand what year 5 or 6 pupils know or do not know about place-value and how they are able to apply their understanding of place-value and the use of operations in this particular context. (Contains 9 tables and 3 figures.)