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

This lesson helps to build procedural skill with counting on from 10. The arithmetic rack is used here because the motion of pushing ten beads beads over at once and saying ten supports the idea of counting on from a known quantity. 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** **model with mathematics as they model how to count on from ten on the arithmetic rack 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:**

- arithmetic rack
- math talk sentence frame
- numeral cards 11-19
- double ten frame or double decker bus template (optional - these can be used in place of the arithmetic rack
- counters (optional)