This lesson is optional. It repeats some of the ideas of Lesson 1 and can be used to reinforce the concept of unitizing a group of ten.

Lesson objective: Understand that ten ones are equal to one group of ten.

Students bring prior knowledge of unitizing a ten from earlier lessons in this unit that teach 1.NBT.2: Understand that the two digits of a two-digit number represent amounts of tens and ones. Understand the following as special cases: a. 10 can be thought of as a bundle of ten ones — called a “ten.”

The concept is developed through work with a tens frame, which shows 10 single items in one unit. Blank ten frames can be found in Additional Materials.

This work helps students deepen their understanding of equivalence because 10 ones are equal to one group of ten, or one ten.

Students engage in Mathematical Practice 7, look for and make use of structure, as they repeatedly make units of ten using objects and draw circles in a tens frame. Students are asked to verbalize the concept of ten ones making one ten. Visualization of one unit of ten is developed as they see, and work with, various representations in the forms of a box of cupcakes, a tens frame, and other "grouped" objects.

**Key vocabulary:**

- bundle
- count
- group
- single
- ten
- ten frame

**Special materials needed:**

- crayons (blue, pink, green, yellow)
- cupcake cards - sheet included
- task instructions - sheet included
- tens frame recording sheet (for coloring cupcakes in task), an optional sheet is included.