Lesson objective: Students will practice their understanding of multiplication. They will recognize the importance of seeing a group of items as a single unit and that a group contains a given number of objects.

Students bring prior knowledge of repeated addition and arrays from 2.OA.03. This prior knowledge is extended to multiplication as students practice with repeated addition and arrays.

The concept is developed through a focus on the idea that unitizing underlies the concept that products of whole numbers can be interpreted as a number of groups of a number of objects. Unitizing requires that students think of a group of some number of objects as "1". For instance, if we think of three groups of four objects, each group of four objects can be thought of as "1".

This work helps students deepen their understanding of operations because students recognize that repeated addition can be thought of as multiplication.

Students engage in Mathematical Practice 4 (model with mathematices) as they create groups, arrays and number lines as an integral part of this lesson.

**Key vocabulary:**

- Array
- Factors
- Multiplication
- Product