Lesson objective: Understand that every number one to nine has a partner such that the two numbers can be composed to make 10.

Students bring prior knowledge of adding by putting together two numbers to make another number from earlier work with K.OA.3. This prior knowledge is extended to adding pairs of numbers to make 10 as students put together different combinations of numbers that make 10. A conceptual challenge students may encounter is incorrectly believing that there is more than exactly one number partner that can make 10 for each number one to nine. Some students may also struggle to correctly count the number of objects they are using to represent the compositions due to a lack of one-to-one correspondence.

The concept is developed through work with a 10-frame, which structures the counting and helps students track the total of 10 objects while also visualizing different combinations to compose 10.

This work helps students deepen their understanding of operations because students are composing numbers pairs to make 10 as a foundation for addition as putting together with larger numbers and developing strategies like bridging 10 for addition and subtraction.

Students engage in Mathematical Practice 7 (Look for and make use of structure) as they develop an understanding of 10 as a foundation for place value understanding.

**Key vocabulary:**

- compose
- decompose
- number bond
- put together
- 10-frame
- 10-strip

**Special materials needed:**

- printed manipulatives of cars and planes (optional)
- 10-frames
- 10-strips
- two-sided counters (commercial or painted lima beans)