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Subtraction as Missing Part — to 20 is a free printable Grade 1 maths worksheet on reaching a subtraction through the addition fact, past ten, aligned to Common Core standard 1.OA.B.4. 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 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 1 of 25 · the same problems every time you open this link.

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One paper per pupil

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All 25 sets ask different questions.

Subtraction as Missing Part — to 20

1.OA.B.4

NameDate

Fill in both blanks.

1.1 + ___ = 24 , so 24 − 1 = ___
2.12 + ___ = 19 , so 19 − 12 = ___
3.7 + ___ = 24 , so 24 − 7 = ___
4.4 + ___ = 21 , so 21 − 4 = ___
5.5 + ___ = 24 , so 24 − 5 = ___
6.6 + ___ = 19 , so 19 − 6 = ___
7.6 + ___ = 25 , so 25 − 6 = ___
8.12 + ___ = 21 , so 21 − 12 = ___
9.11 + ___ = 22 , so 22 − 11 = ___
10.20 + ___ = 24 , so 24 − 20 = ___
11.21 + ___ = 25 , so 25 − 21 = ___
12.5 + ___ = 19 , so 19 − 5 = ___

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

Answer key — Subtraction as Missing Part — to 20

Set 1. Prints on its own sheet.

  1. 1.23 and 23
  2. 2.7 and 7
  3. 3.17 and 17
  4. 4.17 and 17
  5. 5.19 and 19
  6. 6.13 and 13
  7. 7.19 and 19
  8. 8.9 and 9
  9. 9.11 and 11
  10. 10.4 and 4
  11. 11.4 and 4
  12. 12.14 and 14

Questions about Subtraction as Missing Part — to 20

What does the Subtraction as Missing Part — to 20 worksheet cover?

It practises reaching a subtraction through the addition fact, past ten — 12 questions for Grade 1, all on Common Core 1.OA.B.4: See subtraction as finding the missing part. The instruction to pupils is “Fill in both blanks”, and the answer key follows on the next sheet.

Which Common Core standard does Subtraction as Missing Part — to 20 practise?

CCSS.MATH.CONTENT.1.OA.B.4 — 1.OA.B.4, in the Operations & Algebraic Thinking domain 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?

Subtraction as Missing Part — to 20 is written for Grade 1, typically ages 6-7. It is one of the sheets on 1.OA.B.4, so it suits any pupil working at that standard — including older pupils revisiting it and younger ones working ahead.

Does Subtraction as Missing Part — to 20 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 Subtraction as Missing Part — to 20 can I print?

25 — one per pupil, 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 Subtraction as Missing Part — to 20 free to print and photocopy?

Yes. Subtraction as Missing Part — to 20, 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.

Is there a lesson plan to teach 1.OA.B.4?

Yes — “Subtraction as a Missing Part” is a 40-minute Grade 1 plan for 1.OA.B.4, timed section by section, with the misconceptions to expect and an exit ticket. Subtraction as Missing Part — to 20 is the practice that follows it.

More practice for 1.OA.B.4

See subtraction as finding the missing part.

Teaching this next? Subtraction as a Missing Part 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.B.4 of the Common Core State Standards for mathematics.