Lesson objective: Students will be able to compose a ten when adding a two-digit number to a one-digit number.

Students bring prior knowledge of decomposing numbers up to ten from K.OA.A.3. This prior knowledge is extended to composing a ten as students show different ways rocks can be arranged into boxes of ten. A conceptual challenge students may encounter is finding the best way to decompose a number in order to find a combination of ten.

The concept is developed through work with ten frames, which allows students to see how many more are needed to make ten.

This work helps students deepen their understanding of numbers because they practice decomposing numbers in various ways.

Students engage in Mathematical Practice 1: (Make Sense of Problems and Persevere in Solving Them) as they try decomposing numbers in various ways until they find an easy number combination.****

**Key vocabulary:**

- compose
- decompose
- make ten

**Special materials needed:**