The effect of problem format on problem solving strategy selection is investigated within the early algebra domain of functional thinking. Functional Thinking is a type of algebraic reasoning appropriate for elementary students, in which a relationship exists between two sets of values. Three function table problems were given to students in grades two through six (N=232) in three different problem contexts. Problem context affected student strategy selection. Presenting the problem with non-indexical X values elicited the most correct strategy use, whereas the format with indexical X values elicited the most naïve and incorrect strategy use. Presenting the problem in a story context did not help correct strategy selection, but it decreased incorrect strategy use. Findings highlight factors influencing strategy selection, and have implication for instructional design and problem solving.