In this video, we will learn how to
count the sides and vertices of polygons to identify whether or not they’re a
triangle, a quadrilateral, a pentagon, a hexagon, or an octagon.
Polygons are shapes with straight
sides. Which of these two groups of shapes
have straight sides? This shape has straight sides. This shape also has straight
sides. All of the shapes in this group
have straight sides. We can call this group
polygons. The shapes in the second group have
curved sides or some curved sides. These shapes are not polygons.
There are different types of
polygon. To help us identify polygons, we
can count the number of sides and the number of corners. Each of these polygons has three
sides. They also have three corners. The corners or vertices are where
two sides meet. A shape with three sides and three
corners is called a triangle. All of these polygons have four
sides and four corners.
We call four-sided shapes
quadrilaterals. We call shapes with five sides and
five corners or vertices pentagons. We call polygons with six sides and
six corners hexagons. And we call polygons with eight
sides and eight corners octagons. An octopus has eight legs. This is a good way to remember an
octagon has eight sides. Let’s try some questions to help us
practice identifying different polygons by the number of sides and corners.
How many vertices are there in a triangle?
In this question, we’re asked how
many vertices a triangle has. A vertex is another word for
corner, and it’s the point where two lines meet. Let’s draw a triangle to help us
answer the question. How many sides does a triangle
have? One, two, three. Let’s count the number of corners
or vertices. There’s one, two, Three. There are three vertices in a
What is the name of a six-sided
We have to name the polygon with
six sides. Polygons are shapes made from
straight sides, so a six-sided polygon has six straight sides. Let’s sketch a six-sided shape. One, two, three, four, five,
six. A six-sided polygon is called a
What is the name of this shape? Is it an octagon, a pentagon, a
quadrilateral, a triangle, or a hexagon?
An octagon is a shape with eight
sides. A pentagon is a shape with five
sides. A quadrilateral is a four-sided
shape. Triangles have three sides, and
hexagons have six. How many sides does this shape
have? One, two, three, four, five. Which shape has five sides? It’s the pentagon. A polygon with five sides is called
a pentagon. The name of this shape is a
How many more sticks does Matthew
need to change this hexagon into an octagon?
We know that Matthew has made a
hexagon using his sticks. And the question is asking us how
many more sticks will he need to make an octagon. This question is asking us to think
about how many sides a hexagon has and how many sides an octagon has. Hexagons, including Matthew’s
hexagon, have six sides. An octagon has eight sides. What’s the difference between eight
and six? The answer is two. Eight subtract six is two. Matthew will need two more sticks
to change his hexagon into an octagon.
True or false? The number of sides of a polygon is
equal to the number of vertices.
This question is asking us to think
about polygons. We’re being asked if the number of
sides a polygon has is the same as the number of vertices it has. Let’s draw some polygons to help us
think about the question. A triangle is a polygon with three
sides and three corners. So, this polygon has an equal
number of sides and vertices.
Quadrilaterals have four sides and
four corners. The number of sides and vertices
are equal. Pentagons are polygons with five
sides and five corners. The number of sides and vertices is
equal. A hexagon is a polygon with six
sides and six corners. The number of sides and the number
of vertices or corners is equal. And an octagon is a polygon with
eight sides and eight corners or vertices. The number of sides is equal to the
number of vertices. This statement is true. The number of sides of a polygon is
equal to the number of vertices.
What have we learned in this
video? We’ve learned that polygons are
shapes made from straight sides. And we can identify polygons by
counting the number of sides or vertices.