Classifying Triangles by Angle and Side Properties (Marks Included ... - Free Printable

To classify each triangle, we look at two things:
1. Angles – Are all angles less than 90°? (acute) Is one angle exactly 90°? (right) Is one angle greater than 90°? (obtuse)
2. Sides – Are all sides different? (scalene) Are two sides equal? (isosceles) Are all three sides equal? (equilateral)

Let’s go one by one:

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Triangle 1:
- One angle is marked with a square → that’s a right angle (90°).
- All sides look different → scalene.
→ Right Scalene

Triangle 2:
- One angle is wide and open → looks greater than 90° → obtuse.
- All sides look different → scalene.
→ Obtuse Scalene

Triangle 3:
- Has a square mark → right angle.
- Two sides are equal? Wait — no, only one side has a tick, but actually, looking again: it’s a right triangle with legs of different lengths → scalene.
Wait — correction: In triangle 3, the two legs are not marked equal, so it’s scalene.
→ Right Scalene

Triangle 4:
- Has a square → right angle.
- Two sides have matching tick marks → those sides are equal → isosceles.
→ Right Isosceles

Triangle 5:
- No right or obtuse angle → all angles < 90° → acute.
- All three sides have tick marks → all sides equal → equilateral.
→ Acute Equilateral

Triangle 6:
- Looks like all angles are less than 90° → acute.
- All sides look different → scalene.
→ Acute Scalene

Triangle 7:
- All sides have tick marks → all equal → equilateral.
- Equilateral triangles always have 60° angles → acute.
→ Acute Equilateral

Triangle 8:
- One angle is very wide → greater than 90° → obtuse.
- All sides different → scalene.
→ Obtuse Scalene

Triangle 9:
- All angles look less than 90° → acute.
- Two sides have tick marks → isosceles.
→ Acute Isosceles

Triangle 10:
- All angles < 90° → acute.
- Two sides have tick marks → isosceles.
→ Acute Isosceles

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Final Answer:
1. Right Scalene
2. Obtuse Scalene
3. Right Scalene
4. Right Isosceles
5. Acute Equilateral
6. Acute Scalene
7. Acute Equilateral
8. Obtuse Scalene
9. Acute Isosceles
10. Acute Isosceles