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Add Within 1000 — Missing Number is a free printable Grade 3 maths worksheet on finding the missing addend in a three-digit sum, aligned to Common Core standard 3.NBT.A.2. 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 25 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.

Add Within 1000 — Missing Number

3.NBT.A.2

NameDate

Fill in the missing number.

1.124 + ___ = 475
2.466 + ___ = 843
3.229 + ___ = 665
4.206 + ___ = 608
5.332 + ___ = 765
6.106 + ___ = 564
7.333 + ___ = 635
8.270 + ___ = 661
9.143 + ___ = 299
10.439 + ___ = 870
11.151 + ___ = 636
12.418 + ___ = 579

LessonPrint · 3.NBT.A.2 · Set 25 · free to copy for classroom use

Answer key — Add Within 1000 — Missing Number

Set 25. Prints on its own sheet.

  1. 1.351
  2. 2.377
  3. 3.436
  4. 4.402
  5. 5.433
  6. 6.458
  7. 7.302
  8. 8.391
  9. 9.156
  10. 10.431
  11. 11.485
  12. 12.161

More practice for 3.NBT.A.2

Add and subtract within 1000 confidently.

Teaching this next? Fluent Addition and Subtraction to 1000 is the 45-minute plan for it, with the misconceptions to expect.

All Grade 3 worksheets

Last reviewed 2026-09-05. Aligned to 3.NBT.A.2 of the Common Core State Standards for Mathematics.