Objective: We compared Alzheimer's disease (AD) patients' and elderly controls' abilities to select the best strategy on each item and determined whether AD patients tended to repeat the same strategy across consecutive items more often than controls. Method: A total of 60 participants (30 healthy older adults, HOA; 30 AD patients) were asked to select the best rounding strategy to estimate products of multiplication problems (e.g., estimating 42 x 76 by rounding operands down or up, like doing 40 x 70 = 2800 or 50 x 80 = 3200). We identified strategies used on each problem and measured solution latencies and percentage errors with each strategy as a function of problem characteristics. Results: Older adults and AD patients were able to use both available strategies. However, AD patients were less able to select the best strategy than HOA, especially on problems for which selecting the best strategy was most difficult. Moreover, AD patients significantly repeated the preceding strategies across successive problems more often than HOA. Conclusions: Our findings have important implications for further our understanding of dementia-related differences in strategic aspects of cognitive performance.