The paper begins with an examination of the case made for integrating science and mathematics using an approach in which science experiences provide the starting point for developing mathematical concepts and applying schematic knowledge. The project described in this paper began with a design task in which students had to create an economical and healthy food bar which meet certain nutritional specifications. Students were supplied with a table of appropriate nutritional data and an explanation of the way in which it could be used. Students began the task by recalling their knowledge of familiar products, such as muesli bars. This knowledge was used as the basis for an initial formulation which they checked against the specifications using the nutritional data. At this point students were encouraged to set-up a spreadsheet which would make it easy for them to systematically vary the composition of the food bar and thus its price. This proved to be an effective tool for solving this problem in which there were many variables.