CCSS.Math.Content.2.OA.B.2
The standard
Fluently add and subtract within 20 using mental strategies. By end of Grade 2, know from memory all sums of two one-digit numbers.
Common Core State Standards for Mathematics · Operations and Algebraic Thinking
What this standard means
Students need to add and subtract within 20 quickly and accurately, without counting every object one by one. They should use mental strategies like making ten, doubles, near doubles, and using known facts to solve related facts.
Mastery looks like knowing all one-digit addition sums from memory and choosing a useful strategy for subtraction. Students often get stuck counting on their fingers for every problem, mixing up teen numbers, or not seeing that 8 + 7 can become 10 + 5.
Ways to teach it
- Give students ten-frames and counters to build 8 + 6, then move counters to make 10 and name the new fact.
- Ask students to explain which strategy they used for 13 - 8, and have a partner solve it a different way.
- Show five flash cards, such as 9 + 6 or 15 - 7, and have students write answers in one minute.
- Use classroom supply bins to ask, if we have 17 glue sticks and use 9, how many are left?
Plan a lesson for CCSS.Math.Content.2.OA.B.2
Generate a complete lesson plan aligned to this standard, with objectives, activities, and materials. Free, no account needed.
Related standards
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- CCSS.Math.Content.1.OA.C.6
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- CCSS.Math.Content.3.OA.C.7
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