Georgia 2.NR.2.1
The Standard
Fluently add and subtract within 20 using a variety of mental, part-whole strategies.
Georgia's K-12 Mathematics Standards · Apply multiple part-whole strategies, properties of operations and place value understanding to solve real-life, mathematical problems involving addition and subtraction within 1,000.
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students quickly find sums and differences for numbers through 20. They break numbers apart, make 10, use doubles, and connect addition with subtraction.
What Mastery Looks Like
- Students solve mixed facts accurately without counting every object. They can explain choices such as making 10, using doubles, or using addition to solve subtraction.
Common Misconceptions
- Students may count every number from one instead of using known facts. They may treat subtraction as commutative, or misapply doubles and make-ten strategies.
How to Assess It
- Give an exit ticket with 8 + 7, 13 - 6, 9 + 9, and 16 - 8. Students solve mentally and explain one strategy.
Lesson moves
Ways to Teach It
Give pairs two-color counters and ten-frames to model 8 + 7 and 14 - 6, then record how making 10 helped.
Ask, “How could knowing 6 + 6 help you solve 6 + 7 and 13 - 6?”
Play Strategy Match by pairing fact cards with cards labeled make 10, doubles, near doubles, or related addition fact.
Set up a classroom store where students mentally find totals and change for purchases costing no more than 20 cents.
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Printable 2.NR.2.1 Worksheet
A ready-to-print activity worksheet aligned to 2.NR.2.1, with an answer key for the teacher on its own page. No account needed.
PDF, US Letter, prints cleanly in black and white.
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Related Standards
- 1.NR.2.1
Use a variety of strategies to solve addition and subtraction problems within 20.
- 2.NR.2.4
Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.
- 1.NR.2.4
Fluently add and subtract within 10 using a variety of strategies.
- K.NR.5.4
Fluently add and subtract within 5 using a variety of strategies to solve practical, mathematical problems.
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