One of the practical abilities of teachers in elementary education can be found in the teacher's teaching expertise.
Pedagogical Content Knowledges emphasize the professional knowledge that a teacher should possess, which can be seen
as a mixture of educational knowledge and content knowledge. In order to lead a ‘good’ lesson, the teacher should have a sufficient
understanding of subject content and have the ability to explain it in a way that addresses the level of the students. The
purpose of this study is to examine the mathematical content knowledges related to ‘estimation (rounding)’ for elementary
pre-service teachers. Pre-service teachers are not only expected to acquire the necessary knowledge as a teacher but also an
understanding of theory and practice. Lesson Play can be used both as a tool to review the theoretical knowledge of elementary
pre-service teachers and concurrently, as a means of verifying the class lesson. Because Lesson Play is a way of describing
the dialogue between teachers and students in the form of a hypothetical scenario, it is possible to identify the
mathematical content knowledges and misconceptions of elementary pre-service teachers. In this study, through the Lesson
Play of the elementary pre-service teachers written in the 'estimation(rounding)' task, we confirm the various communication
processes that can be activated in the teaching situation and reveal how the student responds to the errors. Lastly, we also analyze
the particular features that Lesson Play brings to the implementation of mathematics lessons.