Lesson objective: Compose the numbers 11-19 by counting on from 10 by 1, 2, 3, 4, 5, 6, 7, 8, or 9.

This lesson helps to build fluency with counting on from 10. Connecting cubes is used here because it supports students' understanding that teen numbers are composed of ten ones and some more ones. This work develops students' understanding that we can count on from 10 by 1, 2, 3, 4, 5, 6, 7, 8, or 9 to reach the numbers 11-19.

Students engage in Mathematical Practice 4:** **Students** **model with mathematics as they model how to count on from ten by 1, 2, 3, 4, 5, 6, 7, 8, or 9 to find the value of the numbers 11-19.

**Key vocabulary:**

- add
- addend
- compose
- count on
- decompose
- sum
- "teen" number

**Special materials needed:**

- connecting cubes
- recording sheet