9 1 I Can Classify Triangles Angles Of Triangles And Congruent ... - Free Printable

Let's solve the problem step by step.

---

Part 1: Match each triangle with its description.

We are given 7 descriptions and 7 labels (A–G). We need to match each description to the correct triangle type.

---

1. Side lengths: 2cm, 4cm, 4cm
- Two sides are equal (4cm, 4cm), so it's isosceles.
- Answer: F. Isosceles

---

2. Side lengths: 3 cm, 2cm, 5cm
- Check if a triangle can be formed:
- 3 + 2 = 5 → This is not greater than 5.
- So, cannot form a triangle (triangle inequality fails).
- Answer: D. Not a triangle

---

3. Side lengths: 1cm, 4cm, 6cm
- Check triangle inequality:
- 1 + 4 = 5 < 6 → Cannot form a triangle.
- Answer: D. Not a triangle

---

4. Side lengths: 4cm, 4cm, 4cm
- All three sides are equal → Equilateral
- Answer: A. Equilateral

---

5. Angle measures: 60°, 60°, 60°
- All angles are equal → Equilateral triangle (also equiangular)
- Answer: A. Equilateral

---

6. Angle measures: 20°, 60°, 90°
- One angle is 90° → Right triangle
- Answer: G. Right

---

7. Angle measures: 20°, 145°, 15°
- Sum = 20 + 145 + 15 = 180° → valid
- One angle is > 90° (145°) → Obtuse triangle
- Answer: C. Obtuse

---

✔ Matching Summary:

| Number | Answer |
|--------|--------|
| 1 | F |
| 2 | D |
| 3 | D |
| 4 | A |
| 5 | A |
| 6 | G |
| 7 | C |

Note: Option B (Scalene) is not used — that’s okay because scalene triangles have all sides different, but none of the descriptions fit that *only* in this list.

---

Part 2: Classify each triangle by its angles and by its sides.

Now, we look at the diagrams:

#### Question 8:
- Triangle with angles: one angle is marked 60°, another 60° → third must be 60° (since sum = 180°)
- All angles = 60° → Equilateral, so also Equiangular
- All sides equal → Equilateral
- Angles: Equilateral (or Equiangular)
- Sides: Equilateral

> But the question asks for classification by angles and by sides.

So:
- Angles: Acute (all < 90°) → but more specifically, equiangular
- However, standard classification by angles: Acute (since all angles < 90°)

But since all angles are equal, it's equiangular, which implies acute.

But typically, we classify as:
- By angles: Acute
- By sides: Equilateral

Wait — let’s clarify:

- By angles: All angles < 90° → Acute
- By sides: All sides equal → Equilateral

But "equilateral" is both a side and angle classification.

So:
- Angles: Acute
- Sides: Equilateral

✔ 8.
- Sides: Equilateral
- Angles: Acute

---

#### Question 9:
- Triangle with right angle (marked with square) → one angle = 90°
- The other two angles: not specified, but clearly not equal (one leg longer than other)
- So, two sides different → Scalene
- One angle is 90° → Right
- So:
- Angles: Right
- Sides: Scalene

✔ 9.
- Sides: Scalene
- Angles: Right

---

#### Question 10:
- Triangle with one angle = 120° → obtuse
- The other two angles are smaller → sum = 60°
- All sides appear different? Let's assume they are (no markings suggesting equality)
- Since one angle > 90° → Obtuse
- If no two sides are equal → Scalene

But we don't have side markings. However, since one angle is 120°, and the others are likely different, unless marked otherwise, assume scalene.

So:
- Angles: Obtuse
- Sides: Scalene

✔ 10.
- Sides: Scalene
- Angles: Obtuse

---

#### Question 11:
- Triangle with two sides marked equal (with tick marks)
- So, Isosceles by sides
- One angle is 90° → Right triangle
- So it's a right isosceles triangle
- Angles: Right
- Sides: Isosceles

✔ 11.
- Sides: Isosceles
- Angles: Right

---

#### Question 12:
- Triangle with all sides marked equal (tick marks on all three sides)
- So: Equilateral
- All angles = 60° → Acute and Equiangular
- So:
- Sides: Equilateral
- Angles: Acute

✔ 12.
- Sides: Equilateral
- Angles: Acute

---

#### Question 13:
- Triangle with one angle = 120° → obtuse
- Two sides marked equal (tick marks)
- So: Isosceles
- One angle > 90° → Obtuse
- So:
- Sides: Isosceles
- Angles: Obtuse

✔ 13.
- Sides: Isosceles
- Angles: Obtuse

---

✔ Final Answers:

#### Part 1: Matching
1. F
2. D
3. D
4. A
5. A
6. G
7. C

#### Part 2: Classify Triangles

| # | Sides | Angles |
|---|-------------|------------|
| 8 | Equilateral | Acute |
| 9 | Scalene | Right |
|10 | Scalene | Obtuse |
|11 | Isosceles | Right |
|12 | Equilateral | Acute |
|13 | Isosceles | Obtuse |

---

Let me know if you'd like this formatted for printing or submission!