In this unit the focus is on solving problems with unknown addends using properties of operations. Students will learn that addition and subtraction are inverse operations, and develop strategies for both.
Key Concepts:
 The commutative property can be applied to addition.
 Subtraction can be thought of as an unknownaddend problem because of the inverse relationship between addition and subtraction.
 We can use strategies such as making ten, counting on, and the relationship between addition and subtraction to add and subtract within 20.
Prior Knowledge Needed:
 Represent and solve an addition/subtraction word problem within 10 (Grade K, Unit 10; K.OA.A.2)
 For any number 19, there is another number that can be added to it to make 10 (Grade K, Unit 12; K.OA.A.4)
 The meaning of addition and/or subtraction doesnâ€™t change when different strategies are used (Grade K, Unit 10; K.OA.A.2)
Units on the Horizon:
 Unit 019 Extending strategies for solving addition and subtraction problems
 Unit 0115: Applying properties of operations to solve problems
 Unit 0118: Demonstrating proficiency in addition and subtraction situations
 Unit 021: Adding and subtracting within 100
Lessons

Lesson objective: Understand the commutative property of addition. Students bring prior knowledge of addition and solving word problems from K.OA.A.2. This prior knowledge is extended to the commutative property of addition as students develop strategie...

Lesson objective: Apply properties of operations to add. This lesson helps to build fluency with addition within 20. Connecting cubes are used because this model supports the development of computational strategies. This work develops students' understa...

Lesson objective: Solve problems using the commutative property of addition. This lesson provides an opportunity for students to apply their knowledge and understanding of the commutative property of addition to a reallife situation. Students are asked...

Lesson objective: Understand that subtraction can be thought of as an unknown addend problem. Students bring prior knowledge of composing and decomposing 10 from K.OA.A.4 This prior knowledge is extended to understanding that addition and subtraction ar...

Lesson objective: Understand that subtraction can be thought of as an unknown addend problem. This lesson helps to build strategies with addition and subtraction. Partpartwhole diagrams and number lines are used here because they show the number partn...

Lesson objective: Solve word problems using addition strategies. This lesson provides an opportunity for students to apply their knowledge and understanding of using a number line and related addition and subtraction facts to a reallife situation. Stud...

Lesson objective: Understand that different strategies can be used to solve addition equations. Students bring prior knowledge of number partners that equal 10 from K.OA.A.4. This prior knowledge is extended to support the addition strategy of making a ...

Lesson objective: Add by using a number line to count on. This lesson helps to build fluency with whole number addition and subtraction. A number line is used because this tool supports the strategy of counting on. This work helps students develop their...

Lesson objective: Add numbers within 20 using the addition strategies. This lesson helps to build fluency with whole number addition. Ten frames and number bonds are used here because they highlight when and how to use the makeaten addition strategy. ...

Lesson objective: Solve problems by using the most efficient computation strategy. This lesson provides an opportunity for students to apply their knowledge and understanding of addition and subtraction strategies to a reallife situation. Students are ...