CCSS 2.OA.2 (Common Core, 2nd Grade): "Fluently add and subtract within 20 using mental strategies. By end of Grade 2, know from memory all sums of two one-digit numbers." The worksheets below practice this standard. Each one is a free printable PDF with an answer key, comes in multiple versions, and can also be assigned digitally - no login or account needed.
Operations and Algebraic Thinking Add and subtract within 20.2Fluently add and subtract within 20 using mental strategies. By end of Grade 2, know from memory all sums of two one-digit numbers.