NC.2.OA.2

Demonstrate mastery by correctly and efficiently solving addition and subtraction problems within 20.

Develop mental math strategies for adding and subtracting. 

Recall basic addition and subtraction facts (e.g., sums and differences within 20) quickly and accurately without the need for calculation. 

Show fluency with sums of 20.

• Use mental strategies: counting on, making ten, decomposing a number leading to a ten, using the relationship between addition and subtraction, creating equivalent but easier or known sums. 

• Know from memory all sums of two one digit numbers 

• Know from memory related subtraction facts of sums of two one-digit numbers. 

There are strategies (counting on, making ten, decomposing a number leading to a ten, using the relationship between addition and subtraction, creating equivalent but easier or known sums) for learning addition and subtraction facts within 20 that will help fluency. 

Fluency is a mixture of knowing some answers, knowing some answers from patterns, and knowing some answers from the use of strategies. 

Basic fact fluency helps students solve more complex mathematical problems.