The purpose of this study was to use multiple data sources, both objective and subjective, to capture students' thinking processes as they were engaged in problem solving, examine the cognitive tool use patterns, and understand what tools were used and why they were used. The findings of this study confirmed previous research and provided clear empirical evidence supporting the theoretical notion that technology-based cognitive tools play an important role in assisting students' problem solving. Students' tool use patterns were discussed in the context of their problem solving. (Contains 3 figures and 3 tables.)