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What Kind of Triangle? is a free printable Grade 4 math worksheet on naming a triangle from its largest angle, aligned to Common Core standard 4.G.A.2. It prints 9 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.

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All 25 sets ask different questions.

What Kind of Triangle?

4.G.A.2

NameDate

Write acute, right or obtuse.

1.A triangle has angles of 15°, 25° and 140°. Is it acute, right or obtuse?
2.A triangle has angles of 85°, 10° and 85°. Is it acute, right or obtuse?
3.A triangle has angles of 90°, 75° and 15°. Is it acute, right or obtuse?
4.A triangle has angles of 10°, 130° and 40°. Is it acute, right or obtuse?
5.A triangle has angles of 80°, 30° and 70°. Is it acute, right or obtuse?
6.A triangle has angles of 50°, 40° and 90°. Is it acute, right or obtuse?
7.A triangle has angles of 90°, 35° and 55°. Is it acute, right or obtuse?
8.A triangle has angles of 90°, 20° and 70°. Is it acute, right or obtuse?
9.A triangle has angles of 10°, 45° and 125°. Is it acute, right or obtuse?

LessonPrint · 4.G.A.2 · Set 1 · free to copy for classroom use

Answer key — What Kind of Triangle?

Set 1. Prints on its own sheet.

  1. 1.obtuse
  2. 2.acute
  3. 3.right
  4. 4.obtuse
  5. 5.acute
  6. 6.right
  7. 7.right
  8. 8.right
  9. 9.obtuse

Questions about What Kind of Triangle?

What does the What Kind of Triangle? worksheet cover?

It practices naming a triangle from its largest angle — 9 questions for Grade 4, all on Common Core 4.G.A.2: Sort shapes by their parallel and perpendicular sides and by their angles, and pick out right triangles. The instruction to students is “Write acute, right or obtuse”, and the answer key follows on the next sheet.

Which Common Core standard does What Kind of Triangle? practice?

CCSS.MATH.CONTENT.4.G.A.2 — 4.G.A.2, under Geometry for Grade 4. The published standard reads: “Classify two-dimensional figures based on the presence or absence of parallel or perpendicular lines, or the presence or absence of angles of a specified size. Recognize right triangles as a category, and identify right triangles.” The worksheet assesses that standard rather than a paraphrase of it.

What age or grade is this worksheet for?

What Kind of Triangle? is written for Grade 4, typically ages 9-10. It is one of the sheets on 4.G.A.2, so it suits any student working at that standard — including older students revisiting it and younger ones working ahead.

Does What Kind of Triangle? come with an answer key?

Yes. All 9 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 What Kind of Triangle? 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 What Kind of Triangle? free to print and photocopy?

Yes. What Kind of Triangle?, 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 4.G.A.2

Sort shapes by their parallel and perpendicular sides and by their angles, and pick out right triangles.

All Grade 4 worksheets

Last reviewed 2026-09-05. Aligned to 4.G.A.2 of the Common Core State Standards for Mathematics.