Before You Begin this Unit…  Unit at a Glance  
Students develop algebraic reasoning in Unit 6. One of the goals for students is to become flexible with the equal sign and to be able to determine the unknown number in a variety of positions (for example, ? + 6 = 10, 10  ? = 6, or 10 = ? + 6). Read page 141, “About the Equal Sign” and “Children’s Understanding of Equality: A foundation for Algebra” and discuss, “What do first grade students need to understand about the equal sign? How does this help students as they further develop algebraic reasoning? Students continue to represent everyday situations with equations and models in Unit 6. The discussions at the start and end of lessons focus on strategies for addition and subtraction and on writing matching equations. Many first grade students become confused when initially representing a subtraction situation. They often reverse the numbers, since they can reverse the parts in an addition equation without changing the meaning. Connect each number and symbol to characters and actions in story problems. 
Suggested Dates: Estimated Duration: 23 Days Investigation 1: 9 lessons including session 1.8A and 1.8B . Investigation 2: 6 including session 2.6A lessons . Investigation 3: 8 lessons


Standards Addressed in the Unit  
Click here for the NCDPI CCSS Unpacking Document This unit focuses on the Operations and Algebraic thinking strand. For more information about this strand and how it should look in the classroom, please visit the Common Core State Standards video series or the link to the unpacking document.
Represent and solve problems involving addition and subtraction.
1.OA.2. Solve word problems that call for addition of three whole numbers whose sum is less than or equal to 20, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.
Understand and apply properties of operations and the relationship between addition and subtraction.
1.OA.4. Understand subtraction as an unknownaddend problem. For example, subtract 10 – 8 by finding the number that makes 10 when added to 8. Add and subtract within 20.
Add and subtract within 20.
1.OA.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).
Work with addition and subtraction equations.
1.OA.8. Determine the unknown whole number in an addition or subtraction equation relating three whole numbers. For example, determine the unknown number that makes the equation true in each of the equations 8 + ? = 11, 5 = _ – 3, 6 + 6 = _. 