This article investigates how students in third grade learn to reason on multiplication when they first encounter that concept in the classroom context. By analysing the data from 24 classrooms focused on teaching and learning multiplication, the article aims at contributing to the research and conceptualisations about how students learn to distinguish multiplicative from additive reasoning in a primary school. A central feature is the strong emphasis students have on addition when they work with multiplication. This emphasis on addition causes tensions in the discussions between the teacher and students. Results are discussed in relation to previous studies of students' multiplicative reasoning and implications for practice are elaborated upon.