**Making Ten** – Kindergarten to first grade. Teacher led lesson on how to decompose the number ten.

**Visualizing Number Combinations** – Kindergarten to first grade. Students see a quick image of a ten frame and share strategies on how the got the number, which is decomposing a number.

**Decompose Numbers Video** – First to Third Grade. Student subtracting two numbers with decomposing.

**Add by Decomposing Numbers** – Second to fourth grade. A lesson to show students on how to add multi-digit numbers by decomposing the numbers.

**Composing & Decomposing Numbers with Base Ten Pieces** – Second to fourth grade. Lesson to watch before you teach.

**CCSS.Math.Content.K.OA.A.3** Decompose numbers less than or equal to 10 into pairs in more than one way, e.g., by using objects or drawings, and record each decomposition by a drawing or equation (e.g., 5 = 2 + 3 and 5 = 4 + 1).

**CCSS.Math.Content.1.OA.A.1** Use addition and subtraction within 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.1

**CCSS.Math.Content.1.OA.C.6** Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 – 4 = 13 – 3 – 1 = 10 – 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 – 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13).

**CCSS.Math.Content.2.OA.B.2** Fluently add and subtract within 20 using mental strategies.2 By end of Grade 2, know from memory all sums of two one-digit numbers.