Why do the name choices change from problem to problem?

The sheet alternates classifying by angles (acute, right, obtuse) with classifying by sides (equilateral, isosceles, scalene). The choices printed with each triangle tell your child which system that problem wants.

What do the tick marks on the sides mean?

Sides with matching ticks are equal. All three sides marked equal means equilateral, exactly two means isosceles, and no matches means scalene. The marks are the evidence, not the look of the drawing.

5th grade classifying triangles

5th grade classifying triangles worksheets

Fifth grade alternates the two naming systems: half the problems classify by angles (acute, right, obtuse) and half by sides (equilateral, isosceles, scalene). One triangle can hold a name from each family, like a right isosceles triangle.

Free printable PDF worksheet, aligned to Common Core 5.G.B.3.

Each print is a different sheet with its own answer key. You don't need to sign up.

The kind of problems you'll get

Classify each triangle as requested. Equal-side marks show equal lengths.

True or false: A scalene triangle can be a right triangle.
Answer: true
True or false: An obtuse triangle can also be a right triangle.
Answer: false
True or false: Every right triangle is acute.
Answer: false

Every print pulls a fresh set of problems at this level, so a make-up test or a second sibling never gets the same sheet.

What's on a 5th grade sheet

The sample sheet above has 10 problems. This sheet is aligned to 5.G.B.3. The 4th grade sheet is aligned to 4.G.A.2.

Classifying triangles. Classify each triangle as requested. Equal-side marks show equal lengths. 10 problems per page.

Every version prints on US Letter or A4, with its answer key after the problems.

How to teach this

Ask which question the problem is asking first, angles or sides, since the printed choices give it away. For side problems, insist on counting tick marks out loud before answering; eyes are unreliable on close lengths. A good stretch conversation: can a triangle be right and isosceles at the same time? Draw one together and the question settles itself.

Watch for: Kids call a triangle obtuse because it looks big. The classification is about one angle's size, not the whole triangle's. Kids skip the tick marks and eyeball the sides. Equal sides are shown by matching ticks, not by how long the sides look.

Common questions about 5th grade classifying triangles

Why do the name choices change from problem to problem?: The sheet alternates classifying by angles (acute, right, obtuse) with classifying by sides (equilateral, isosceles, scalene). The choices printed with each triangle tell your child which system that problem wants.
What do the tick marks on the sides mean?: Sides with matching ticks are equal. All three sides marked equal means equilateral, exactly two means isosceles, and no matches means scalene. The marks are the evidence, not the look of the drawing.

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Aligned to Common Core 5.G.B.3. Reviewed by the One more sheet team. Content version 240, updated September 2026.

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