1.OA.B. Understand and apply properties of operations and the relationship between addition and subtraction.

• Fact Families
• Fact Families with Pictures

1.OA.B.3. Apply properties of operations as strategies to add and subtract.Students need not use formal terms for these properties. 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.)

• Domino Addition
• Doubles?

1.OA.B.4. Understand subtraction as an unknown-addend problem. For example, subtract $10 - 8$ by finding the number that makes 10 when added to 8.

• Cave Game Subtraction