Grade 6 Triangles and their Properties

Interactive step-by-step solver for understanding triangles and their properties.

Grade 6 Triangles and their Properties

Step-by-Step Learning

Learn about triangles and their properties through these example problems with detailed step-by-step solutions.

Example 1: Classifying a Triangle by Sides

A triangle has sides of 5 cm, 5 cm, and 6 cm. Classify the triangle by its sides.

Step 1: Identify the sides:

Sides are 5 cm, 5 cm, and 6 cm.

Step 2: Check the triangle inequality:

Sum of any two sides must be greater than the third side:

5 + 5 > 6 (10 > 6, true),

5 + 6 > 5 (11 > 5, true),

5 + 6 > 5 (11 > 5, true).

Step 3: Classify by sides:

Since two sides are equal (5 cm = 5 cm), the triangle is isosceles.

Step 4: Therefore, the triangle is isosceles.
Sides: 5 cm, 5 cm, 6 cm Triangle Inequality: 5+5>6, 5+6>5, 5+6>5 Two sides equal (5=5) Result: Isosceles triangle

Example 2: Classifying a Triangle by Angles

A triangle has angles of 40°, 60°, and 80°. Classify the triangle by its angles.

Step 1: Identify the angles:

Angles are 40°, 60°, and 80°.

Step 2: Check the angle sum property:

\( 40^\circ + 60^\circ + 80^\circ = 180^\circ \), which is true.

Step 3: Classify by angles:

All angles are less than 90° (40°, 60°, 80°), so the triangle is acute-angled.

Step 4: Therefore, the triangle is acute-angled.
Angles: 40°, 60°, 80° Sum: \( 40^\circ + 60^\circ + 80^\circ = 180^\circ \) All angles < 90° Result: Acute-angled triangle

Example 3: Finding the Third Angle

A triangle has angles of 50° and 70°. Find the third angle.

Step 1: Identify the given angles:

Angles are 50° and 70°.

Step 2: Use the angle sum property:

The sum of angles in a triangle is \( 180^\circ \).

\( \text{Third angle} = 180^\circ - (\text{Angle 1} + \text{Angle 2}) \).

Step 3: Calculate the third angle:

\( \text{Third angle} = 180^\circ - (50^\circ + 70^\circ) = 180^\circ - 120^\circ = 60^\circ \).

Step 4: Therefore, the third angle is 60°.
Angles: 50°, 70° Angle Sum: \( 180^\circ \) Third Angle: \( 180^\circ - (50^\circ + 70^\circ) = 60^\circ \) Result: 60°

Example 4: Using the Exterior Angle Property

A triangle has two interior angles of 40° and 60°. Find the exterior angle adjacent to the third angle.

Step 1: Identify the given interior angles:

Interior angles are 40° and 60°.

Step 2: Use the exterior angle property:

An exterior angle equals the sum of the two non-adjacent interior angles.

Step 3: Calculate the exterior angle:

\( \text{Exterior angle} = 40^\circ + 60^\circ = 100^\circ \).

Step 4: Verify by finding the third interior angle:

Third angle = \( 180^\circ - (40^\circ + 60^\circ) = 80^\circ \).

Exterior angle = \( 180^\circ - 80^\circ = 100^\circ \), which matches.

Step 5: Therefore, the exterior angle is 100°.
Interior Angles: 40°, 60° Exterior Angle Property Exterior Angle: \( 40^\circ + 60^\circ = 100^\circ \) Result: 100°

Example 5: Real-World Problem

Design a triangular garden with sides 3 m, 4 m, and 5 m. Classify the triangle.

Step 1: Identify the sides:

Sides are 3 m, 4 m, and 5 m.

Step 2: Check the triangle inequality:

3 + 4 > 5 (7 > 5, true),

3 + 5 > 4 (8 > 4, true),

4 + 5 > 3 (9 > 3, true).

Step 3: Classify by sides:

All sides are different (3 ≠ 4 ≠ 5), so the triangle is scalene.

Step 4: Check for a right angle (Pythagorean theorem):

\( 3^2 + 4^2 = 9 + 16 = 25 \), and \( 5^2 = 25 \).

Since \( 3^2 + 4^2 = 5^2 \), the triangle is right-angled.

Step 5: Therefore, the triangle is right-angled and scalene.
Sides: 3 m, 4 m, 5 m All sides different: Scalene Pythagorean: \( 3^2 + 4^2 = 5^2 \) Result: Right-angled, Scalene

Practice Mode

Enter your own triangle problem, and get a step-by-step solution.

Note: This solver handles classifying triangles by sides (e.g., Sides 5 cm, 5 cm, 6 cm; classify triangle by sides), classifying by angles (e.g., Angles 40°, 60°, 80°; classify triangle by angles), finding the third angle (e.g., Angles 50°, 70°; find third angle), finding an exterior angle (e.g., Interior angles 40°, 60°; find exterior angle), and real-world problems (e.g., Sides 3 m, 4 m, 5 m; classify triangle). Enter the problem clearly.

Use formats like 'Sides 5 cm, 5 cm, 6 cm; classify triangle by sides', 'Angles 40°, 60°, 80°; classify triangle by angles', 'Angles 50°, 70°; find third angle', 'Interior angles 40°, 60°; find exterior angle', or 'Sides 3 m, 4 m, 5 m; classify triangle'.