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Missing Number — Adding to 20 is a free printable Grade 1 maths worksheet on the unknown in an addition crossing ten, aligned to Common Core standard 1.OA.D.8. It prints 9 questions with an answer key on its own sheet of paper, in 25 versions that each ask different questions, so no two pupils in the class work from the same page. Print it from the browser or download it as a PDF — no account, no email.

Set 10 of 25 · the same problems every time you open this link.

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One paper per pupil

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Set 1 has all 25 in a single PDF. All 25 sets ask different questions.

Missing Number — Adding to 20

1.OA.D.8

NameDate

Work out each answer.

1.___ + 7 = 15
2.___ + 7 = 14
3.___ + 6 = 13
4.___ + 9 = 16
5.___ + 9 = 18
6.___ + 9 = 15
7.___ + 8 = 17
8.___ + 7 = 13
9.___ + 8 = 14

LessonPrint · 1.OA.D.8 · Set 10 · free to copy for classroom use

Answer key — Missing Number — Adding to 20

Set 10. Prints on its own sheet.

  1. 1.8
  2. 2.7
  3. 3.7
  4. 4.7
  5. 5.9
  6. 6.6
  7. 7.9
  8. 8.6
  9. 9.6

More practice for 1.OA.D.8

Find the missing number in a number sentence.

Teaching this next? Finding the Missing Number is the 40-minute plan for it, with the misconceptions to expect.

All Grade 1 worksheets

Last reviewed 2026-09-05. Aligned to 1.OA.D.8 of the Common Core State Standards for mathematics.