Grade 1 · 40 problems · sums within 20; missing addend, sums within 20 · includes answer key · CCSS.1.OA.C.6
Most first graders add the small facts by counting on, then lose the count once the sum crosses 10. Addition within 20 has 20 facts: 6 with a sum of 10 or less, 10 that cross 10, and 4 that use a teen. No sum on that sheet is over 20. Missing addends within 20 shows the total and one addend, and the child writes the partner. Take 3 + 8 from the first sheet. The next number after 3 is 4. If a child counts 3 as one of the 8 steps, they land on 10, which is one too small. On the missing-addend sheet, kids often write the total in the blank. Cover the blank and ask what the whole is before they write. A ten-frame helps when they run out of fingers.
Addition within 20
Grade 1 · 20 problems · sums within 20 · includes answer key · CCSS.1.OA.C.6