During Unit 1, Operations and Algebraic Thinking, your children will develop strategies for adding and subtracting whole numbers based on their prior work with small numbers. They will use a variety of models, including discrete objects and lengthbased models (e.g., cubes connected to form lengths), to model addto, takefrom, puttogether, takeapart, and compare situations to develop meaning for the operations of addition and subtraction, and to develop strategies to solve arithmetic problems with these operations. Your children will understand connections between counting and addition and subtraction (e.g., adding two is the same as counting on two). They will 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, your children will build their understanding of the relationship between addition and subtraction.
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Key Vocabulary:
Children need to:
 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.
Solving Word Problems 
Solving Comparison Type Word Problems 
Using Tools to Solve 
 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
Adding 3 Addends 
Word Problems with 3 Addends 
 Organize, represent, and interpret data with up to three categories; ask and answer questions about the total number of data points, how many in each category, and how many more or less are in one category than in another.
Using a Bar Graph 
Representing Data 
Addition and Subtraction of Data 
 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.)
Associative Property 
Commutative Property 
 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.
Unknown Addend 
Addition and Subtraction 
Minus Mission 
 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 = _
Matching Math 
Ace of Numbers 
HTB Missing Part 
 Relate counting to addition and subtraction (e.g., by counting on 2 to add 2).
 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).
HTB Make 10 
MPG Making 10 
 Understand the meaning of the equal sign, and determine if equations involving addition and subtraction are true or false. For example, which of the following equations are true and which are false? 6 = 6, 7 = 8 –1, 5 + 2 = 2 + 5, 4 + 1 = 5 + 2.
Understanding Equals 
Balancing Equations 

