CCSS.Math.Content.3.OA.D.8
The standard
Solve two-step word problems using the four operations. Represent these problems using equations with a letter standing for the unknown quantity. Assess the reasonableness of answers using mental computation and estimation strategies including rounding.
Common Core State Standards for Mathematics · Operations and Algebraic Thinking
What this standard means
Students need to solve word problems that take two operations, such as add then multiply, or subtract then divide. They should write an equation with a letter for the unknown, not just compute. They also need to explain why their answer makes sense using estimation, rounding, or mental math.
Mastery looks like choosing the right operations, keeping track of what the unknown means, and checking the answer against the story. Students often get stuck by doing only the first step, using numbers in order without thinking, or writing an equation that does not match the problem.
Ways to teach it
- Give pairs 24 counters and a two-step story card, then have them model, write an equation with a letter, and solve.
- Ask students to write, 'I know my answer is reasonable because...' after solving a two-step lunch money problem.
- Use an exit ticket with one two-step word problem, one equation with a letter, and one estimation check.
- Show a grocery receipt and ask students to find the total cost of multiple items, then figure out change from $20.
Plan a lesson for CCSS.Math.Content.3.OA.D.8
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