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Adding to 100 — Mixed is a free printable Grade 1 math worksheet on judging two-digit sums, with the unmade ten as the trap, aligned to Common Core standard 1.NBT.C.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 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.

Adding to 100 — Mixed

1.NBT.C.4

NameDate

Write true or false. If false, write the right answer.

1.True or false? 21 + 9 = 30
2.True or false? 85 + 5 = 90
3.True or false? 29 + 9 = 28
4.True or false? 29 + 3 = 32
5.True or false? 11 + 9 = 10
6.True or false? 45 + 6 = 51
7.True or false? 55 + 6 = 51
8.True or false? 33 + 7 = 40
9.True or false? 37 + 5 = 32
10.True or false? 28 + 4 = 32
11.True or false? 43 + 8 = 41
12.True or false? 16 + 8 = 14

LessonPrint · 1.NBT.C.4 · Set 1 · free to copy for classroom use

Answer key — Adding to 100 — Mixed

Set 1. Prints on its own sheet.

  1. 1.true
  2. 2.true
  3. 3.false — 38
  4. 4.true
  5. 5.false — 20
  6. 6.true
  7. 7.false — 61
  8. 8.true
  9. 9.false — 42
  10. 10.true
  11. 11.false — 51
  12. 12.false — 24

Questions about Adding to 100 — Mixed

What does the Adding to 100 — Mixed worksheet cover?

It practices judging two-digit sums, with the unmade ten as the trap — 12 questions for Grade 1, all on Common Core 1.NBT.C.4: Add numbers up to 100. The instruction to students is “Write true or false. If false, write the right answer”, and the answer key follows on the next sheet.

Which Common Core standard does Adding to 100 — Mixed practice?

CCSS.MATH.CONTENT.1.NBT.C.4 — 1.NBT.C.4, under Number & Operations in Base Ten for Grade 1. The published standard reads: “Add within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of 10.” The worksheet assesses that standard rather than a paraphrase of it.

What age or grade is this worksheet for?

Adding to 100 — Mixed is written for Grade 1, typically ages 6-7. It is one of the sheets on 1.NBT.C.4, so it suits any student working at that standard — including older students revisiting it and younger ones working ahead.

Does Adding to 100 — 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 Adding to 100 — 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 Adding to 100 — Mixed free to print and photocopy?

Yes. Adding to 100 — 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.NBT.C.4

Add numbers up to 100.

All Grade 1 worksheets

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