OR.1.2. Number and Operations and Algebra: Develop understandings of addition and subtraction and strategies for basic addition facts and related subtraction facts.
1.2.1. Model ''part-whole,'' ''adding to,'' ''taking away from,'' and ''comparing'' situations to develop an understanding of the meanings of addition and subtraction.
1.2.2. Develop and use efficient strategies for adding and subtracting whole numbers using a variety of models, including discrete objects, length-based models (e.g., lengths of connecting cubes) and number lines.
1.2.3. Apply with fluency sums to 10 and related subtraction facts.
1.2.4. Use the concept of commutative , associative [(4 + 3) + 7 = 4 + (3 + 7)], and identity [0 + 3 = 3] properties of addition to solve problems involving basic facts.