Triangles

Content Triangles
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Triangles

Do you know what a slice of watermelon and a slice of pizza have in common?

They both have the shape of a triangle! What exactly does this mean? If you want to find out more about triangles, continue reading.

What Are the Properties of a Triangle?

Properties of shapes are certain attributes the shape must have to be called that particular shape. The geometric properties of triangles are that they must be a closed shape that has three sides and three vertices.

However, certain attributes do not matter, such as the size of a triangle or the colour. We can get lots of different triangles, as long as they have three sides and three vertices.

Triangles – Summary

Triangles must ...

• ... have three sides:

• ... have three vertices:

Triangles can ...

• ... be any size:

• ... be any colour:

• ... face in any direction:

Continue your learning with our triangles interactive exercises and worksheets.

TranscriptTriangles

Nico and Nia are having lunch at their favorite restaurant, Three Sides Cafe. “I am SOOO hungry, Nia!” “MEEEE TOOOO!” "“Everything looks delicious!” “How are we going to choose what to eat?” " We can order the Three Sides Special." "What is the Three Sides Special?" "It is any food on the menu that is a triangle shape!" "But how will we know which food is a triangle?" We can help Nico and Nia order their lunch by finding foods that are in the shape of Triangles A triangle is a shape. Shapes are two-dimensional figures that we can name based on their properties. Properties are characteristics that a shape MUST HAVE to be called that particular shape.

Let's look at a triangle. The properties of a triangle are that it must be a closed shape that has three sides and three corners or vertices. Shapes must have particular properties to be called that shape, however, there are some things that do not matter. When deciding which shape a figure is we might notice other things but they don't always have to be the same. For example, the SIZE might be different. "A triangle can be big, big, BIG!" "or a triangle can be small,small, small." The colour might also be different. Triangles can be ANY colour!

Triangles can also face in many different directions or orientations.

Let's identify some triangles! Is this a triangle? Start by counting the sides. It has one, two, three sides. Now count the corners or vertices. It has one, two, three vertices. Yes, this shape is a triangle! How about this shape? Is this shape a triangle? Start by counting the sides. One, two, three, FOUR. Wait a minute, this shape has FOUR sides! Since we know that triangles MUST have three sides, we know that this is NOT a triangle! Let’s try ONE more! Count the sides. Count the vertices. Yes, this is a triangle because it has all of the necessary properties. Now that we know all the properties of a triangle, let’s help Nico and Nia find which foods to order for lunch. Look at the menu! Can you point to all of the foods that are triangle shaped? Here’s one! This slice of pizza! This slice of pizza has all of the properties of a triangle! Here is another one! A triangle is made by this half of a sandwich! There is one on this slice of cake! "And the last one is found from this slice of watermelon!" Remember, shapes must have certain properties to be able to be called that shape. A triangle is a closed shape that always has three sides and three corners or vertices.

But, a triangle can be any size or colour and face any direction. "Yum! This lunch is delicious!" "Yes! It's TRI-iffic!"

Triangles exercise

Would you like to apply the knowledge you’ve learnt? You can review and practice it with the tasks for the video Triangles.
• Help Nico remember what he learnt about triangles.

Hints

This is an example of a triangle.

Count the sides and vertices of this triangle.

Solution

Properties are characteristics that a shape must have.
A triangle has 3 sides.
A triangle has 3 vertices. //

• Identify the triangles in Nico's artwork!

Hints

Triangles have 3 sides and 3 vertices.

Triangles can be different sizes and colours and can face in different directions.

There are 5 triangles in the picture.

Solution

There are 5 hidden triangles in Nico's artwork.
Triangles have:

• 3 sides
• 3 vertices
Triangles can be different:
• sizes
• colours
• can face in different directions

• How many triangles do you see?

Hints

A triangle has 3 sides and 3 vertices.

These are examples of triangles.
Triangles can be different colours and shapes and face in different directions.

Solution

There are 3 triangles in the picture.
These shapes have:

• 3 sides
• 3 vertices

• How many triangles do you see in each picture?

Hints

Triangles have 3 sides and 3 vertices.

These are examples of triangles.

Solution

A triangle is a closed shape with 3 sides and 3 vertices.
The house has 1 triangle.
The kite has 4 triangles.
The boat has 2 triangles.
The desert has 3 triangles.

• Which shape is a triangle?

Hints

A triangle is not round.

A triangle does not have 4 sides.

Solution

This is a triangle.
A triangle has

• 3 sides
• 3 vertices

• Which shape am I?

Hints

Properties are characteristics that a shape must have.

Counting the number of sides and vertices can help you work out the shape.

Solution

A square has:

• 4 sides that are all the same length
• 4 vertices

A triangle has:

• 3 sides
• 3 vertices

A circle is round. It has:

• no sides
• no vertices

A rectangle has:

• 4 sides
• 4 vertices
• two pairs of opposite sides that are equal in length