USING STRUCTURE TO FIND THE DISTANCE ON AN EMPTY NUMBER LINE.

Looking for and making use of structure along with using the mathematical tools (i.e., number line) are important mathematical practices. In this paper, we explore 32 first-grade and 36 thirdgrade students' noticing and making use of the structure of two identical number lines when determining the distance of a bunny's jumps. The number lines represented a distance from 11 to 27, and students could choose to jump to 20 (nearest multiple of ten), 21 (adding ten), or 15 (nearest multiple of five). Choosing 21 (distance of 10) was the most frequent choice, and overall, 71% of third graders' and 17% of first graders' attempts showed a correct distance. However, less than one-third of students made connections between their two number lines and noticed their structure. This study informs the importance of number combination knowledge and highlighting structure in order to leverage efficient addition strategies. [ABSTRACT FROM AUTHOR]