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Missing Numbers — Mixed is a free printable Grade 1 math worksheet on the unknown anywhere in either operation, aligned to Common Core standard 1.OA.D.8. It prints 12 questions with an answer key on its own sheet of paper, in 25 versions that each ask different questions, so no two students in the class work from the same page. Print it from the browser or download it as a PDF — no account, no email.

Set 1 of 25 · the same problems every time you open this link.

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All 25 sets ask different questions.

Missing Numbers — Mixed

1.OA.D.8

NameDate

Work out each answer.

1.___ + 8 = 15
2.___ + 9 = 16
3.___ + 3 = 12
4.___ + 6 = 9
5.___ + 5 = 10
6.___ + 4 = 8
7.___ − 2 = 9
8.___ − 8 = 5
9.___ − 9 = 10
10.___ − 14 = 1
11.___ − 6 = 4
12.___ − 7 = 11

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

Answer key — Missing Numbers — Mixed

Set 1. Prints on its own sheet.

  1. 1.7
  2. 2.7
  3. 3.9
  4. 4.3
  5. 5.5
  6. 6.4
  7. 7.11
  8. 8.13
  9. 9.19
  10. 10.15
  11. 11.10
  12. 12.18

Questions about Missing Numbers — Mixed

What does the Missing Numbers — Mixed worksheet cover?

It practices the unknown anywhere in either operation — 12 questions for Grade 1, all on Common Core 1.OA.D.8: Find the missing number in a number sentence. The instruction to students is “Work out each answer”, and the answer key follows on the next sheet.

Which Common Core standard does Missing Numbers — Mixed practice?

CCSS.MATH.CONTENT.1.OA.D.8 — 1.OA.D.8, under Operations & Algebraic Thinking for Grade 1. The published standard reads: “Determine the unknown whole number in an addition or subtraction equation relating three whole numbers.” The worksheet assesses that standard rather than a paraphrase of it.

What age or grade is this worksheet for?

Missing Numbers — Mixed is written for Grade 1, typically ages 6-7. It is one of the sheets on 1.OA.D.8, so it suits any student working at that standard — including older students revisiting it and younger ones working ahead.

Does Missing Numbers — Mixed come with an answer key?

Yes. All 12 answers are generated from the same problems as the questions, so the key cannot drift out of step with the sheet. It starts on a fresh sheet of paper, after the questions, so it is not handed out with the class by accident.

How many different versions of Missing Numbers — Mixed can I print?

25 — one per student, and all 25 ask different questions. Set 1 downloads the whole class as a single PDF. Every version is fixed to its own address, so a sheet printed today holds the same problems when you reopen it next week.

Is Missing Numbers — Mixed free to print and photocopy?

Yes. Missing Numbers — Mixed, its answer key and its 25 versions are free to print and photocopy for your own class, with no account, no email capture and no subscription at the download step. Please do not resell them or republish them as your own.

More practice for 1.OA.D.8

Find the missing number in a number sentence.

All Grade 1 worksheets

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