CCSS.Math.Content.1.OA.A.1
The Standard
Use addition and subtraction within 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.
Common Core State Standards for Mathematics · Operations and Algebraic Thinking
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students decide whether a story involves joining, separating, combining, or comparing amounts. They use counters, drawings, and equations to find a missing number at the beginning, middle, or end.
What Mastery Looks Like
- Students solve story problems within 20 when the missing number appears in any position. They show the situation with objects, a drawing, and an equation, then explain what each number represents.
Common Misconceptions
- Students may choose an operation from a keyword instead of thinking about the action in the story. They may put the answer after the equal sign every time or subtract numbers in the order given.
How to Assess It
- Use this exit ticket: “Mia had some apples. She gave away 6 and has 8 left. How many did she start with?” Require a drawing and an equation with a box for the missing number.
Lesson moves
Ways to Teach It
Give pairs 20 counters and story cards, then have them act out each story and record a matching equation.
Ask, “How are 12 birds with 5 flying away different from 5 birds joining 7 birds?” and compare equations.
Play Missing Number Match by pairing story cards with equation cards such as 9 + □ = 14 or □ − 4 = 7.
Count classroom pencils, hide some in a bag, and have students find the hidden amount from the starting and remaining totals.
Free download
Printable 1.OA.A.1 Worksheet
A ready-to-print activity worksheet aligned to CCSS.Math.Content.1.OA.A.1, with an answer key for the teacher on its own page. No account needed.
PDF, US Letter, prints cleanly in black and white.
Download the worksheetLearning progression
Where This Standard Sits
See the whole path on the Operations & Algebraic Thinking progression map.
Before This Standard
If students are struggling here, check these first.
- CCSS.Math.Content.K.OA.A.1
Students must represent joining, separating, and equations before solving varied addition and subtraction word problems with unknowns within 20.
- CCSS.Math.Content.K.CC.B.5
Counting sets within 20 supports modeling and checking add-to, take-from, and compare problems with objects, but equations can develop alongside it.
- CCSS.Math.Content.K.OA.A.2
Solving simple add and subtract stories within 10 supports larger numbers, more problem types, and unknown positions within 20.
What This Unlocks
Mastery here sets students up for these next.
- CCSS.Math.Content.2.OA.A.1
Students must understand addition and subtraction story structures, unknown positions, and equations before extending them to 100 and two-step problems.
- CCSS.Math.Content.2.MD.D.10
Solving graph questions uses the same put-together, take-apart, and compare addition and subtraction situations in a new data display context.
- CCSS.Math.Content.1.OA.A.2
Two-number addition word problem models and equations support representing and solving three-addend situations within 20.
- CCSS.Math.Content.2.MD.A.4
Comparing lengths uses the same take-apart or comparison thinking to find the difference between two measured amounts.
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