Explore, understand, and apply the commutative and associative properties as strategies for solving addition problems.
Share, discuss, and compare strategies as a class.
Connect counting on to solving subtraction problems. For the problem “15 – 7 = ?” they think about the number they have to count on from 7 to get to 15.
Work with sums and differences less than or equal to 20 using the numbers 0 to 20.
Identify and then apply a pattern or structure in mathematics. For example, pose a string of addition and subtraction problems involving the same three numbers chosen from the numbers 0 to 20, such as 4 + 13 = 17 and 13 + 4 = 17.
Analyze number patterns and create conjectures or guesses.
Choose other combinations of three numbers and explore to see if the patterns work for all numbers 0 to 20.
Understand that addition and subtraction are related and that subtraction can be used to solve problems where the addend is unknown.
Use the strategies of counting on and counting back to understand number relationships.
Organize and record results using tallies and tables.
Determine the initial and the change unknown.
Students will develop strategies for adding and subtracting whole numbers based on their prior work with small numbers. They use a variety of models, including discrete objects and length-based models (e.g., cubes connected to form lengths), to model add-to, take-from, put-together, take-apart, and compare situations. They will use these models to develop meaning for the operations of addition and subtraction and to develop strategies to solvearithmeticc problems with these operations. Prior to first grade students should recognize that any given group of objects (up to 10) can be separated into sub groups in multiple ways and remain equivalent in amount to the original group (Ex: A set of 6 cubes can be separated into a set of 2 cubes and a set of 4 cubes and remain 6 total cubes).
Students understand connections between counting and addition and subtraction (e.g., adding two is the same as counting on two). They use properties of addition to add whole numbers and to create and use increasingly sophisticated strategies based on these properties (e.g., ―making tens) to solve addition and subtraction problems within 20. By comparing a variety of solution strategies, children build their understanding of the relationship between addition and subtraction. (Ohio DOE)
The standard MGSE1.OA.3 expects teachers to use their understanding of the commutative and associative properties when teaching addition. The students are NOT expected to name or memorize these properties. First grade teachers are laying the foundation and building an understanding of these properties so that students can have formal discussions and utilize names of the properties in later grades