Reasoning and constructing mathematical explanations for an audience have become increasingly important activities in elementary classrooms with the implementation of reform-oriented curriculum and standards. Mobile learning tools and applications, such as screencasts, allow students to generate multimedia presentations of their solution strategies. Nine elementary students were interviewed as they generated screencasts to solve mathematics problems on a mobile tablet. A rubric was used to analyze 45 student-generated screencasts to investigate the characteristics of their explanations. The majority of students constructed explanations that described the procedures of their direct modeling strategies. Students' determination to be understood by the viewer appears to be a viable prediction for this approach. Students also provided evidence of attending to the audience in other ways, such as assuming teacher personas and adjusting their explanations to improve clarity.