Teaching Matrix Multiplication with Impactful and Productive Meaning

What is the meaning of matrix multiplication? In this article, I outline a sequence of lessons for an introductory linear algebra course to teach matrix multiplication with impactful and productive meaning. These lessons are part of a broader linear algebra curriculum I have developed centered around students developing core mathematical mental actions such as meaning-making, symbolizing, interpreting, and justifying. For each lesson, I provide goals, a lesson plan, and an explanation of my instructional choices.