## 2.NBT.B.9

## Explain why addition and subtraction strategies work, using place value and the properties of operations. (Explanations may be supported by drawings or objects.)

45 Lesson(s)

#### The big idea of this lesson is the understanding that addition can be represented as parts of a whole and that we can use addition sentences to represent those parts.

#### The big idea of this lesson is that students can solve for near doubles by thinking of the related doubles fact.

#### Making ten is one of the foundational strategies for developing flexible numerical thinking, accuracy, and efficiency.

Big Idea: