CCSS.Math.Content.2.OA.A
The standard
Represent and solve problems involving addition and subtraction.
Common Core State Standards for Mathematics
What this standard means
Students need to make sense of story problems, choose addition or subtraction, and show their thinking with drawings, equations, or objects. They should work with situations that involve joining, separating, comparing, and finding missing parts, not just keywords.
Mastery looks like a student explaining why a problem matches 36 + 18 or 54 - 18, including when the unknown is at the start or middle. Students often get stuck by grabbing numbers and adding them, ignoring what the story is asking. They also mix up comparison problems and missing addend problems.
Ways to teach it
- Use counters and two-color mats to act out join, take away, and missing part stories before writing matching equations.
- Ask students, “What is happening in the story, and what are we trying to find?” before they choose an operation.
- Give one word problem and three equations, then have students circle the match and explain their choice in one sentence.
- Use a classroom supply scenario, such as crayons passed out and crayons left, to write and solve a subtraction story.
Plan a lesson for CCSS.Math.Content.2.OA.A
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Related standards
- CCSS.Math.Content.1.OA.D
Work with addition and subtraction equations.
- CCSS.Math.Content.3.OA.A
Represent and solve problems involving multiplication and division.
- CCSS.Math.Content.1.OA.A
Represent and solve problems involving addition and subtraction.
- CCSS.Math.Content.K.OA.A.2
Solve addition and subtraction word problems, and add and subtract within 10, e.g., by using objects or drawings to represent the problem.