NY Next Generation Math NY-2.OA.2.b

Math2nd GradeAdd and subtract within 20.

The Standard

Know from memory all sums within 20 of two one-digit numbers.

New York State Next Generation Mathematics Learning Standards

Teacher's field guide

What Students Need to Do: Students recall every sum of two one-digit numbers without counting or rebuilding each sum. They answer facts within 20 accurately and promptly.
What Mastery Looks Like: The student gives sums such as 8 + 7 and 9 + 6 from memory. The student recalls facts in varied order instead of relying on a memorized sequence.
Common Misconceptions: Students may confuse knowing facts from memory with recounting on fingers. They may also reverse an addend or answer with a nearby subtraction fact.
How to Assess It: Show ten mixed addition facts with one-digit addends, including 8 + 7 and 9 + 6. Ask the student to answer each without counting tools.

Lesson moves

Sort fact cards into known instantly, almost known, and needs practice piles, then revisit the last two piles.
Ask students to explain which related facts helped them remember 7 + 8.
Play a partner flash-card game that mixes sums within 20 in a different order each round.
Use quick mental totals for pairs of classroom supplies, such as 8 pencils and 6 markers.

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