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**In This Unit of Study…**

Students demonstrate procedural fluency as they use strategies such as counting on, making ten, decomposing a number leading to ten, using the relationship between addition and subtraction, and creating equivalent but easier sums to solve addition and subtraction problems. They will be expected to apply the associative and commutative properties of addition, especially within adding three or more whole numbers; however, they are not expected to name these properties or use parentheses. Students will restate a subtraction problem as a missing addend problem while also determining the unknown whole number in an addition or subtraction equation that relates three whole numbers. Students relate their strategy to a written method and communicate their thinking. Students use their understanding of the equal sign to determine whether equations involving addition and subtraction are true or false.

**B.E.S.T. Benchmarks:**

- MA.1.NSO.2.2 Add two whole numbers with sums from 0 to 20 and subtract using related facts with procedural reliability.
- MA.1.AR.1.1 Apply properties of addition to find a sum of three or more whole numbers.
- MA.1.AR.2.1 Restate a subtraction problem as a missing addend problem using the relationship between addition and subtraction.
- MA.1.AR.2.2 Determine and explain if equations involving addition or subtraction are true or false.
- MA.1.AR.2.3 Determine the unknown whole number in an addition or subtraction equation, relating three whole numbers, with the unknown in any position.

**Key Concepts:**

- I can use the strategies of adding to, putting together, comparing, and taking from when I add or subtract within 20.
- I can apply properties of operations as strategies to add and subtract. (These properties include knowing how to use the commutative property and the associative property.)
- I can use my understanding of the relationship between addition and subtraction (for example, knowing that 8 + 4 = 12, one knows 12 – 8 = 4) to add and subtract within 20.
- I understand subtraction as an unknown addend problem.
- I understand the meaning of the equal sign and can determine if equations involving addition and subtraction are true or false.
- I understand that the sum or difference can be on either side of the equal sign in an equation with no more than four terms.
- I can determine the unknown whole number in an addition or subtraction equation, relating three whole numbers, with the unknown in any position.
- I can use a symbol to represent the unknown in an addition or subtraction equation.
- I can explain the meaning of the equal sign and determine if equations involving addition and subtraction are true.
- I can determine the unknown whole number in an addition or subtraction equation relating three whole numbers. (For example, I can determine the unknown number that makes the equation true.)

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