This paper describes a case study in which one woman in a focus group of 11 women recounted her use of numerical and mathematical tools in her personal and work life. According to the researcher, the subject's experiences engendered strong feelings and revealed that aspects of her self-identity were bound up with her use of tools and feelings about them. In addition, the interplay between socio-cultural factors and the subject's mode of thinking shaped the strategies she chose to address problems that arose. She was competent at using calculators, computers, and maps and at programming video recorders. But she panicked when she had to mentally calculate prices, take money, and give change. The researcher distinguishes between serialist and holistic thinking to explain these differences. When the subject was able to see numerical and mathematical problems holistically she was able to grasp them, but when a serial operation such as making change was required, she had difficulties. The subject's self-identity was both influenced and formed by the situations she was in and it is the interplay between her thinking and the culture that produces her differing facilities with numerical and mathematical tools. (Includes 8 references.) (MO)