Lesson objective: Connect decomposing a total into number partners to patterns found in these pairs.

This lesson provides an opportunity for students to apply their knowledge and understanding of decomposition to a mathematical situation. Students are asked to play a game, record number partners for five, and look for patterns or repeating pairs.

Key Concept students will use:

- The same number can be decomposed in more than one way.

Skills students will use:

- Counting one-to-one (Grade K, Unit 1)
- Counting to tell "how many" are in a set of objects (Grade K, Unit 1)
- Understanding that arrangement and order of objects counted does not affect the total of a set (Grade K, Unit 2)
- Understanding that a total can be decomposed into number partners
- Understanding that a total can have more than one set of number partners

Students engage in Mathematical Practice 5 (Reason abstractly and quantitatively) as they record the number partners for each round of play and reason about how a number can be decomposed in more than one way. Students may need to be asked how many cups they begin each round with and how this relates to the pairs of numbers they record on their record sheet. Additionally, students engage in Mathematical Practice 8 (Look for and express regularity in repeated reasoning) as they make sense of repeated pairs or turn around pairs discovered during play.

**Key vocabulary: **

- combinations
- number partners
- pattern
- pair
- record
- take apart

**Special materials needed:**

- ball
- cups
- record sheet (or another option to record thinking)