NY Next Generation Math NY-2.OA.2.a
The Standard
Fluently add and subtract within 20 using mental strategies. Strategies could include: counting on, making ten, decomposing a number leading to a ten, using the relationship between addition and subtraction, and creating equivalent but easier or known sums.
New York State Next Generation Mathematics Learning Standards
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students add and subtract within 20 accurately, efficiently, and flexibly using mental strategies. They may count on, make ten, decompose to ten, use related facts, or create an easier equivalent sum.
What Mastery Looks Like
- The student solves 8 + 6 by making 10 and solves 13 - 4 by stepping through 10. The student chooses a useful strategy without needing every fact memorized.
Common Misconceptions
- Students may think fluency means answering instantly or using only memorized facts. They may apply a strategy mechanically without preserving the value of the expression.
How to Assess It
- Give six mixed facts within 20, including 8 + 7 and 14 - 6. Ask students to solve mentally and explain two strategies.
Lesson moves
Ways to Teach It
Use ten-frames and counters to practice making ten, decomposing through ten, and connecting related facts.
Ask students which mental strategy fits 9 + 6 best and why.
Play strategy switch, solving fact cards with two different mental methods before keeping the card.
Mentally update small attendance or supply totals as amounts are added and removed within 20.
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Related Standards
- NY-3.NBT.2
Fluently add and subtract within 1,000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition ...
- NY-2.NBT.5
Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.
- NY-1.OA.6.a
Add and subtract within 20. Use strategies such as: counting on, making ten, decomposing a number leading to a ten, using the relationship between addition and ...
- NY-1.OA.6.b
Fluently add and subtract within 10.
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