**Objective: **

Understand that a number can be put together or taken apart in more than one way.

This optional activity can be used instead of or in support of Unit 6 Lesson 7.

**Math concept addressed:**

In this Guided Collaborative Task, students will use their knowledge and understanding of decomposition to figure out that a number can be taken apart in more than one way and still maintain a total equal to the original set. Students will figure this out with direct modeling using color tiles, which can be bundled, piled, and grouped as a single unit to support counting and cardinality.

Under the “Additional materials” tab, you’ll find grid paper that may be used as students color in or shade the smaller parts they see within the total.

**Prior knowledge needed: **

Students bring prior knowledge of composing a value. This prior knowledge is extended to include decomposing and taking apart as students develop an understanding that a number can be taken apart in more than one way.

**How students will collaborate:**

Collaboration happens through a collaborative structure called "Back to Back". Students will take turns describing their representations and visualizing what each other's work looks like based on the descriptions.

**Mathematical practice featured:**

Students engage in Mathematical Practice 7 (Look for and make use of structure) as they explore different arrangements of five tiles and share how the design can be seen or explained in terms of smaller parts of the total, such as groups of two or body sections of an imaginative animal.

**Key vocabulary:**

- number partners

- subtraction

- take apart

- total

**Special materials needed:**

- grid paper (optional)