In this innovative study, Jean Lave moves the analysis of one particular form of cognitive activity — arithmetic problem-solving — out of the laboratory and into the domain of everyday life. In so doing, she shows how mathematics in the "real world", such as that entailed in grocery shopping or dieting, is, like all thinking, shaped by the dynamic encounter between the culturally-endowed mind and its total context, a subtle interaction that shapes both the human subject and the world within which it acts.