Operations and Algebraic Thinking

Add and subtract within 20.
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.) (Students need not use formal terms for these properties.)
Tasks
1.OA Task 10a; 1.OA 10a Student Form
1.OA Task 10b; 1.OA 10b Student Form

1.OA.4 Understand subtraction as an unknown-addend problem. For example, subtract 10 – 8 by finding the number that makes 10 when added to 8. Add and subtract within 20.
Tasks
Standard 1.OA.4 is assessed under 1.OA.1 when students solve Add To/Change Unknown and Put Together/Take Apart/Addend Unknown tasks.