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Sort Triangles by Angles is a free printable Grade 4 math worksheet on acute, right and obtuse triangles from their angles, aligned to Common Core standard 4.G.A.2. It prints 5 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.

Sort Triangles by Angles

4.G.A.2

NameDate

Sort each one into the right box.

1.Sort each one into the right box.

Sort: angles of 45°, 65° and 70°, angles of 90°, 45° and 45°, angles of 70°, 60° and 50°, angles of 120°, 30° and 30°

Acute triangleRight triangleObtuse triangle
2.Sort each one into the right box.

Sort: angles of 120°, 30° and 30°, angles of 90°, 30° and 60°, angles of 60°, 60° and 60°, one angle wider than a square corner

Acute triangleRight triangleObtuse triangle
3.Sort each one into the right box.

Sort: angles of 90°, 45° and 45°, angles of 120°, 30° and 30°, angles of 20°, 90° and 70°, angles of 90°, 30° and 60°

Acute triangleRight triangleObtuse triangle
4.Sort each one into the right box.

Sort: angles of 90°, 30° and 60°, angles of 25°, 130° and 25°, angles of 100°, 50° and 30°, one angle wider than a square corner

Acute triangleRight triangleObtuse triangle
5.Sort each one into the right box.

Sort: one square corner, angles of 90°, 30° and 60°, angles of 90°, 45° and 45°, angles of 60°, 60° and 60°

Acute triangleRight triangleObtuse triangle

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

Answer key — Sort Triangles by Angles

Set 1. Prints on its own sheet.

  1. 1.Acute triangle: angles of 45°, 65° and 70°, angles of 70°, 60° and 50°; Right triangle: angles of 90°, 45° and 45°; Obtuse triangle: angles of 120°, 30° and 30°
  2. 2.Acute triangle: angles of 60°, 60° and 60°; Right triangle: angles of 90°, 30° and 60°; Obtuse triangle: angles of 120°, 30° and 30°, one angle wider than a square corner
  3. 3.Acute triangle: —; Right triangle: angles of 90°, 45° and 45°, angles of 20°, 90° and 70°, angles of 90°, 30° and 60°; Obtuse triangle: angles of 120°, 30° and 30°
  4. 4.Acute triangle: —; Right triangle: angles of 90°, 30° and 60°; Obtuse triangle: angles of 25°, 130° and 25°, angles of 100°, 50° and 30°, one angle wider than a square corner
  5. 5.Acute triangle: angles of 60°, 60° and 60°; Right triangle: one square corner, angles of 90°, 30° and 60°, angles of 90°, 45° and 45°; Obtuse triangle: —

Questions about Sort Triangles by Angles

What does the Sort Triangles by Angles worksheet cover?

It practices acute, right and obtuse triangles from their angles — 5 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 “Sort each one into the right box”, and the answer key follows on the next sheet.

Which Common Core standard does Sort Triangles by Angles 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?

Sort Triangles by Angles 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 Sort Triangles by Angles come with an answer key?

Yes. All 5 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 Sort Triangles by Angles 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 Sort Triangles by Angles free to print and photocopy?

Yes. Sort Triangles by Angles, 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 4.G.A.2?

Yes — “Classifying Shapes by Lines and Angles” is a 50-minute Grade 4 plan for 4.G.A.2, timed section by section, with the misconceptions to expect and an exit ticket. Sort Triangles by Angles is the practice that follows it.

More practice for 4.G.A.2

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

Teaching this next? Classifying Shapes by Lines and Angles is the 50-minute plan for it, with the misconceptions to expect.

All Grade 4 worksheets

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