In Topic D students solve two kinds of division situations—partitive (group size unknown) and measurement (number of groups unknown)—using factors of 2 and 3. The tape diagram is introduced in Lesson 11 as a tool to help students recognize and distinguish between types of division. By the end of Lessons 11 and 12 students independently draw and label tape diagrams that help them to compare and analyze problems that may use the same division sentence, but have quotients representing different things.
Lesson 13 solidifies growing understanding that the unknown can also be found from the related multiplication sentence. Students initially work through word problems using arrays and tape diagrams to practice solving the two types of division, then transition to problem solving using abstract division and multiplication equations.