CCSS.Math.Content.2.OA.A.1
The standard
Use addition and subtraction within 100 to solve one- and two-step word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using drawings and equations with a symbol for the unknown number to represent the problem.
Common Core State Standards for Mathematics · Operations and Algebraic Thinking
What this standard means
Students need to read a word problem, figure out what is happening, and choose addition or subtraction within 100. They should handle one-step and two-step problems, including missing start, change, result, part, whole, or comparison amounts. They need to show thinking with drawings, number lines, equations, or a symbol for the unknown.
Mastery looks like matching the story to an equation and explaining why it works. Students often get stuck when the unknown is not at the end, when a problem has two steps, or when comparison language sounds like addition but needs subtraction.
Ways to teach it
- Hands-on activity: Give pairs 30 counters and story cards, then have them build each problem before writing a matching equation with a box for the unknown.
- Discussion prompt: Ask, “What is changing in this story, and what number are we trying to find?” before students solve.
- Quick assessment: Show one two-step word problem and ask students to draw it, write an equation, and circle the unknown.
- Real-world connection: Use a classroom supply problem about pencils given out, pencils returned, and pencils left to model a two-step situation.
Plan a lesson for CCSS.Math.Content.2.OA.A.1
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Related standards
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Use addition and subtraction within 100 to solve word problems involving lengths that are given in the same units, e.g., by using drawings (such as drawings of ...
- CCSS.Math.Content.1.OA.A.1
Use addition and subtraction within 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, wit...
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Solve word problems that call for addition of three whole numbers whose sum is less than or equal to 20, e.g., by using objects, drawings, and equations with a ...
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Solve addition and subtraction word problems, and add and subtract within 10, e.g., by using objects or drawings to represent the problem.