Classifying triangles by sides and angles worksheet with numbered diagrams for identifying triangle types.

Let’s go through each triangle one by one and classify them based on the instructions.

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Part 1: Classify by Sides (Equilateral, Isosceles, Scalene)

We look for tick marks on the sides — they show which sides are equal.

- Triangle 1: No tick marks → all sides different → Scalene
- Triangle 2: Two sides have one tick mark each → two sides equal → Isosceles
- Triangle 3: No tick marks → all sides different → Scalene
- Triangle 4: All three sides have one tick mark → all sides equal → Equilateral
- Triangle 5: Two sides have one tick mark each → two sides equal → Isosceles
- Triangle 6: No tick marks → all sides different → Scalene

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Part 2: Classify by Angles (Acute, Right, Obtuse)

We look at the angle symbols:
- A square corner = right angle (90°)
- An arc with no special mark = acute (<90°) or obtuse (>90°) — we judge by shape
- If all angles look sharp → acute
- If one angle looks wide (wider than a right angle) → obtuse
- If one angle has a square → right

- Triangle 7: All angles have arcs, none look wide → all acute → Acute
- Triangle 8: One angle has an arc that looks wider than 90° → Obtuse
- Triangle 9: Has a square corner → Right
- Triangle 10: One angle has an arc that looks wider than 90° → Obtuse
- Triangle 11: Has a square corner → Right
- Triangle 12: One angle has an arc that looks wider than 90° → Obtuse

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