Before You Begin this Unit…  Unit at a Glance  
In Grade K, students had experience with addition and subtraction situations within 10. They should have developed an understanding that, in addition problems, when sets of numbers are joined together they make a new set. Students should be able to model addition and subtraction by using manipulatives. This unit has an early focus on counting accurately and there is explicit discussion about what can go wrong to make a count inaccurate. This lays the foundation for student selfassessment and selfcorrection. This is also an opportunity for teachers to formatively assess students counting for accuracy and organization and to identify students for which this may be an area for intervention. The mathematical focus of this unit is on building number sense through counting and comparing quantities, and through composing and decomposing numbers. Students also work with the operations, developing strategies for combining quantities. An early focus on how to approach a story problem is emphasized in this unit and makes clear to students the target of accurately solving a problem first by understanding what the problem is asking. This is also an opportunity for teachers to formatively assess how a student approaches a problem and if this is an area that might require intervention for students. An early focus on clear written and oral communication through sharing of student work makes this ongoing target clear to students and offers them a road to success. Teachers are able to formatively assess if this is an area in which students will need intervention. 
Suggested Dates:August 25October 1Estimated Duration: 27 daysInvestigation 1: 4 lessonsInvestigation 2: 7 lessonsInvestigation 3: 7 lessonsInvestigation 4: 7 lessons 

Standards Addressed in the Unit  
Click here for the NCDPI CCSS Unpacking Document • Count a set of up to 20 objects. • Compare and order quantities to 12. • Combine two small quantities. • Interpret (retell the action and sequence) and solve addition story problems. • Find more than one combination of two addends for a number up to 10 (e.g., 7 is 4 and 3 and also 5 and 2). 1.OA.1. Use addition and subtraction within 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem. 1.OA.3. Apply properties of operations as strategies to add and subtract.^{2} Examples: If 8 + 3 = 11 is known, then 3 + 8 = 11 is also known. (Commutative property of addition.) To add 2 + 6 + 4, the second two numbers can be added to make a ten, so 2 + 6 + 4 = 2 + 10 = 12. (Associative property of addition.) 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. 1.NBT.3 Compare two twodigit numbers based on meanings of the tens and ones digits, recording the results of comparisons with the symbols >, =, and <. Additional CCSS addressed in this unit: Extend the counting sequence. 1.NBT.1 Develop place value understanding. 1.NBT.2, 1.NBT.3 Solve addition and subtraction word problems. 1.OA.2 Develop addition and subtraction skills. 1.OA.5, 1.OA.6 Work with addition and subtraction equations. 1.OA.7, 1.OA.8 