The goal of this study was to determine whether adult students incarcerated at a large correctional facility in New England use the provided scientific calculator appropriately when taking the Official GED Practice Test in mathematics. 13 students were interviewed after taking a practice test and asked for their strategy for solving each problem. The test items were then compared against a typology to determine appropriate calculator use. The students used the calculator very infrequently, and when they did, they preferred to use it on questions for which alternative strategies would be less effective. On problems which could be solved equally well with or without a calculator, these students most often chose the latter. This is likely due to many years of performing calculations mentally, a skill which many have honed to quite sophisticated levels. When using the calculator, these students were much less accurate in their responses; it is possible that fully integrating the calculator into investigative activities may help them make better use of the technology. (Contains 2 figures and 7 tables.)