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Mixed Missing Numbers is a free printable Grade 1 math worksheet on the unknown in any of the three positions, aligned to Common Core standard 1.OA.B.4. It prints 15 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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One paper per student

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All 25 sets ask different questions.

Mixed Missing Numbers

1.OA.B.4

NameDate

Work out each answer.

1.___ + 5 = 8
2.___ + 9 = 15
3.___ + 8 = 12
4.___ + 8 = 13
5.___ + 6 = 8
6.6 + ___ = 15
7.4 + ___ = 13
8.7 + ___ = 13
9.6 + ___ = 10
10.4 + ___ = 10
11.14 − ___ = 11
12.19 − ___ = 7
13.8 − ___ = 3
14.12 − ___ = 4
15.14 − ___ = 2

LessonPrint · 1.OA.B.4 · Set 1 · free to copy for classroom use

Answer key — Mixed Missing Numbers

Set 1. Prints on its own sheet.

  1. 1.3
  2. 2.6
  3. 3.4
  4. 4.5
  5. 5.2
  6. 6.9
  7. 7.9
  8. 8.6
  9. 9.4
  10. 10.6
  11. 11.3
  12. 12.12
  13. 13.5
  14. 14.8
  15. 15.12

Questions about Mixed Missing Numbers

What does the Mixed Missing Numbers worksheet cover?

It practices the unknown in any of the three positions — 15 questions for Grade 1, all on Common Core 1.OA.B.4: See subtraction as finding the missing part. The instruction to students is “Work out each answer”, and the answer key follows on the next sheet.

Which Common Core standard does Mixed Missing Numbers practice?

CCSS.MATH.CONTENT.1.OA.B.4 — 1.OA.B.4, under Operations & Algebraic Thinking for Grade 1. The published standard reads: “Understand subtraction as an unknown-addend problem.” The worksheet assesses that standard rather than a paraphrase of it.

What age or grade is this worksheet for?

Mixed Missing Numbers is written for Grade 1, typically ages 6-7. It is one of the sheets on 1.OA.B.4, so it suits any student working at that standard — including older students revisiting it and younger ones working ahead.

Does Mixed Missing Numbers come with an answer key?

Yes. All 15 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 Mixed Missing Numbers 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 Mixed Missing Numbers free to print and photocopy?

Yes. Mixed Missing Numbers, 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.B.4

See subtraction as finding the missing part.

All Grade 1 worksheets

Last reviewed 2026-09-05. Aligned to 1.OA.B.4 of the Common Core State Standards for Mathematics.