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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 21 of 25 · the same problems every time you open this link.

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One paper per student

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Set 1 has all 25 in a single PDF. 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 60°, 60° and 60°, angles of 100°, 50° and 30°, angles of 80°, 50° and 50°, angles of 25°, 130° and 25°

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

Sort: one angle wider than a square corner, angles of 60°, 60° and 60°, angles of 70°, 60° and 50°, one square corner

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

Sort: one angle wider than a square corner, angles of 80°, 50° and 50°, angles of 20°, 90° and 70°, angles of 100°, 50° and 30°

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

Sort: angles of 90°, 45° and 45°, angles of 60°, 60° and 60°, one angle wider than a square corner, one square corner

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

Sort: one angle wider than a square corner, angles of 120°, 30° and 30°, one square corner, angles of 90°, 45° and 45°

Acute triangleRight triangleObtuse triangle

LessonPrint · 4.G.A.2 · Set 21 · free to copy for classroom use

Answer key — Sort Triangles by Angles

Set 21. Prints on its own sheet.

  1. 1.Acute triangle: angles of 60°, 60° and 60°, angles of 80°, 50° and 50°; Right triangle: —; Obtuse triangle: angles of 100°, 50° and 30°, angles of 25°, 130° and 25°
  2. 2.Acute triangle: angles of 60°, 60° and 60°, angles of 70°, 60° and 50°; Right triangle: one square corner; Obtuse triangle: one angle wider than a square corner
  3. 3.Acute triangle: angles of 80°, 50° and 50°; Right triangle: angles of 20°, 90° and 70°; Obtuse triangle: one angle wider than a square corner, angles of 100°, 50° and 30°
  4. 4.Acute triangle: angles of 60°, 60° and 60°; Right triangle: angles of 90°, 45° and 45°, one square corner; Obtuse triangle: one angle wider than a square corner
  5. 5.Acute triangle: —; Right triangle: one square corner, angles of 90°, 45° and 45°; Obtuse triangle: one angle wider than a square corner, angles of 120°, 30° and 30°

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.

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