CCSS.Math.Content.1.OA.C.6
The Standard
Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 - 4 = 13 - 3 - 1 = 10 - 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 - 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13).
Common Core State Standards for Mathematics · Operations and Algebraic Thinking
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students add and subtract numbers with answers within 20. They use efficient strategies and become quick and accurate with facts whose answers are within 10.
What Mastery Looks Like
- Students answer addition and subtraction facts within 10 quickly and accurately. They solve problems within 20 by counting on, making ten, breaking apart numbers, or using related facts.
Common Misconceptions
- Students may count every object instead of counting on from the larger number. They may change the total when moving parts to make ten. Some know an addition fact but do not connect it to related subtraction facts.
How to Assess It
- Give students 8 + 7, 14 - 6, 6 + 4, and 9 - 3. Ask them to solve each and draw or write one strategy.
Lesson moves
Ways to Teach It
Build 8 + 7 with counters on ten-frames, move two counters to fill the first frame, then record 10 + 5 = 15.
Ask, “How are 8 + 6 and 14 - 8 connected?” Have students explain with a drawing and two equations.
Play a partner card game where students draw two number cards, add them, then name a related subtraction fact.
Set up a classroom store where students find totals and change within 20 using coins, counters, or price cards.
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Printable 1.OA.C.6 Worksheet
A ready-to-print activity worksheet aligned to CCSS.Math.Content.1.OA.C.6, 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.2
Solving and representing addition and subtraction within 10 supports the facts and meanings needed for fluent strategies within 20.
- CCSS.Math.Content.1.OA.C.5
Counting on and counting back are core strategies students use before fluency and more advanced within-20 strategies.
- CCSS.Math.Content.K.OA.A.4
Finding complements to 10 directly supports make-ten addition and subtraction strategies within 20, though students can also use other strategies.
What This Unlocks
Mastery here sets students up for these next.
- CCSS.Math.Content.2.OA.B.2
Grade 2 fact fluency within 20 depends on Grade 1 strategies like making ten, decomposing, and inverse relationships.
- CCSS.Math.Content.2.NBT.B.5
Within-20 facts, making tens, and addition-subtraction relationships support efficient two-digit strategies within 100.
- CCSS.Math.Content.1.NBT.C.4
Within-20 facts, making ten, and decomposition support composing a ten and explaining two-digit addition strategies within 100.
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