Lesson objective: Understand that a group of objects can be organized in an array.

Students bring prior knowledge of equal groups using odd and even numbers from 2.OA.3. This prior knowledge is extended to arrays as students organize groups of objects into an array with equal rows and columns. A conceptual challenge students may encounter is thinking that the number of objects in each row and column do not have to be equal.

The concept is developed through work with groups of objects, which can be arranged into an array to represent given numbers.

This work helps students deepen their understanding of equivalence. It is important for the groups of objects in each row and column of an array to be equal.

Students engage in Mathematical Practice 6 (Attend to precision) as they compose two-dimensional shapes as a collection of rows and as a collection of columns of objects, which requires students to be precise in their representations.

**Key vocabulary:**

- arrange
- array
- column
- equal
- group
- objects
- row