CCSS.Math.Content.1.OA.B.4
The Standard
Understand subtraction as an unknown-addend 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 rewrite a subtraction problem as a missing-addend equation. They find the missing number by asking what must be added to the known part to make the whole.
What Mastery Looks Like
- A student can solve 10 - 8 by writing 8 + ? = 10 and finding 2. The student can check the answer by showing that 8 + 2 = 10.
Common Misconceptions
- Some students count the starting number as the first backward count, causing an answer that is one too small. Others cannot connect 10 - 8 to 8 + ? = 10, or they add 10 and 8 instead.
How to Assess It
- Give this exit ticket: “Solve 13 - 9. Write a missing-addend equation, then draw a picture that proves your answer.”
Lesson moves
Ways to Teach It
Give pairs 10 counters, have one partner hide 7, and ask the other to write 7 + ? = 10 and find the hidden amount.
Ask, “How can 8 + ? = 12 help you solve 12 - 8?” and have students draw and explain their thinking.
Play Missing Partner by revealing a total card and one part card, then having students write the matching addition and subtraction equations.
Present a bus with 15 seats and 11 riders, then find the empty seats by completing 11 + ? = 15.
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Printable 1.OA.B.4 Worksheet
A ready-to-print activity worksheet aligned to CCSS.Math.Content.1.OA.B.4, 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
Representing addition and subtraction situations gives students the meanings needed to see a subtraction fact as a missing addend.
- CCSS.Math.Content.K.OA.A.2
Solving small addition and subtraction problems with objects gives the concrete part-whole experience needed to see subtraction as missing addend.
- CCSS.Math.Content.K.OA.A.3
Decomposing numbers into two parts supports seeing subtraction as finding the missing part in an addition pair.
What This Unlocks
Mastery here sets students up for these next.
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Related Standards
- CCSS.Math.Content.1.OA.B
Understand and apply properties of operations and the relationship between addition and subtraction.
- CCSS.Math.Content.2.OA.A
Represent and solve problems involving addition and subtraction.
- CCSS.Math.Content.K.OA.A
Understand addition as putting together and adding to, and understand subtraction as taking apart and taking from.
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