Triangle Worksheets - Math Monks - Free Printable

Let's solve the problem step by step.

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Part 1: Classify triangles by angles (acute, obtuse, right)

We classify triangles based on their angles:

- Right triangle: One angle is exactly 90°
- Obtuse triangle: One angle is greater than 90°
- Acute triangle: All angles are less than 90°

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#### Triangle 1
Angles: 45°, 90°, 45°
→ Has a 90° angle → Right triangle

✔ Answer: Right

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#### Triangle 2
Angles: 60°, 60°, 60°
→ All angles < 90° → Acute triangle

✔ Answer: Acute

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#### Triangle 3
Angles: 140°, 40°, 10°
→ One angle > 90° (140°) → Obtuse triangle

✔ Answer: Obtuse

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#### Triangle 4
Angles: 50°, 92°, 38°
→ One angle > 90° (92°) → Obtuse triangle

✔ Answer: Obtuse

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#### Triangle 5
Angles: 40°, 60°, 80°
→ All angles < 90° → Acute triangle

✔ Answer: Acute

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#### Triangle 6
Angles: 60°, 50°, 70°
→ All angles < 90° → Acute triangle

✔ Answer: Acute

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✔ Part 1 Summary:

| # | Type |
|---|-------------|
| 1 | Right |
| 2 | Acute |
| 3 | Obtuse |
| 4 | Obtuse |
| 5 | Acute |
| 6 | Acute |

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Part 2: Classify triangles by sides (equilateral, isosceles, scalene)

We classify based on side lengths:

- Equilateral: All three sides equal
- Isosceles: Two sides equal
- Scalene: All sides different

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#### Triangle 7
Sides: 4 cm, 5 cm, 6 cm
→ All sides different → Scalene

✔ Answer: Scalene

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#### Triangle 8
Sides: 4.5 in, 7.5 in, 6.5 in
→ All sides different → Scalene

✔ Answer: Scalene

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#### Triangle 9
Sides: 9 yd, 12 yd, 9 yd
→ Two sides equal (9 yd) → Isosceles

✔ Answer: Isosceles

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#### Triangle 10
Sides: 4.5 cm, 4.5 cm, 4.5 cm
→ All sides equal → Equilateral

✔ Answer: Equilateral

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#### Triangle 11
Sides: 4 cm, 11 cm, 12 cm
→ All sides different → Scalene

✔ Answer: Scalene

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#### Triangle 12
Sides: 3.5 cm, 6 cm, 3.5 cm
→ Two sides equal (3.5 cm) → Isosceles

✔ Answer: Isosceles

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✔ Part 2 Summary:

| # | Type |
|---|--------------|
| 7 | Scalene |
| 8 | Scalene |
| 9 | Isosceles |
|10 | Equilateral |
|11 | Scalene |
|12 | Isosceles |

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✔ Final Answers:

#### By Angles:
1. Right
2. Acute
3. Obtuse
4. Obtuse
5. Acute
6. Acute

#### By Sides:
7. Scalene
8. Scalene
9. Isosceles
10. Equilateral
11. Scalene
12. Isosceles

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