Classify Triangles (worksheets, printable, online, answers) - Free Printable

Let's solve the triangle classification problem step by step. We are asked to classify each triangle by side lengths and by angle measurements.

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🔹 Triangle Classification Basics

#### ✔ By Side Lengths:
- Equilateral: All three sides are equal.
- Isosceles: Two sides are equal.
- Scalene: No sides are equal.

#### ✔ By Angle Measurements:
- Acute: All angles are less than 90°.
- Right: One angle is exactly 90° (right angle).
- Obtuse: One angle is greater than 90°.

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Now, let’s go through each triangle in the image.

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🔸 First Set of Triangles (Top Table)

#### a.
- Image: A triangle with no marked sides equal, and one angle appears to be acute. No right angle symbol.
- Side Lengths: All sides look different → Scalene
- Angles: All angles appear less than 90° → Acute
- ✔ Answer:
- Side: Scalene
- Angle: Acute

#### b.
- Image: A triangle with two sides marked as equal (with tick marks), and a base. Looks like an isosceles triangle.
- Side Lengths: Two sides equal → Isosceles
- Angles: All angles appear less than 90° → Acute
- ✔ Answer:
- Side: Isosceles
- Angle: Acute

#### c.
- Image: A triangle with a right angle symbol (square corner) at one vertex.
- Side Lengths: Sides look different → Scalene
- Angles: One angle is 90° → Right
- ✔ Answer:
- Side: Scalene
- Angle: Right

#### d.
- Image: A triangle with two sides marked equal (tick marks), and one angle looks larger than 90°.
- Side Lengths: Two sides equal → Isosceles
- Angles: One angle is clearly greater than 90° → Obtuse
- ✔ Answer:
- Side: Isosceles
- Angle: Obtuse

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🔸 Second Set of Triangles (Bottom Table)

#### a.
- Image: A triangle with a right angle symbol.
- Side Lengths: All sides appear different → Scalene
- Angles: One angle is 90° → Right
- ✔ Answer:
- Side: Scalene
- Angle: Right

#### b.
- Image: A triangle with no equal sides marked, and all angles appear less than 90°.
- Side Lengths: All sides different → Scalene
- Angles: All angles < 90° → Acute
- ✔ Answer:
- Side: Scalene
- Angle: Acute

#### c.
- Image: A triangle with two sides marked equal (tick marks), and one angle appears greater than 90°.
- Side Lengths: Two sides equal → Isosceles
- Angles: One angle > 90° → Obtuse
- ✔ Answer:
- Side: Isosceles
- Angle: Obtuse

#### d.
- Image: A triangle with all three sides marked equal (three tick marks).
- Side Lengths: All sides equal → Equilateral
- Angles: In equilateral triangles, all angles are 60° → Acute
- ✔ Answer:
- Side: Equilateral
- Angle: Acute

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✔ Final Answers:

| Letter | Side Lengths | Angle Measurements |
|--------|------------------|--------------------|
| a. | Scalene | Acute |
| b. | Isosceles | Acute |
| c. | Scalene | Right |
| d. | Isosceles | Obtuse |

| Letter | Side Lengths | Angle Measurements |
|--------|------------------|--------------------|
| a. | Scalene | Right |
| b. | Scalene | Acute |
| c. | Isosceles | Obtuse |
| d. | Equilateral | Acute |

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📌 Summary:

- Equilateral ⇒ All sides equal, all angles = 60° → always acute
- Isosceles ⇒ Two sides equal; can be acute, right, or obtuse
- Scalene ⇒ No equal sides; can be any angle type
- Right ⇒ One 90° angle
- Obtuse ⇒ One angle > 90°
- Acute ⇒ All angles < 90°

You should circle the correct options for each row accordingly. Let me know if you'd like this formatted as a printable answer sheet!