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What is a Pentagon?

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What is a Pentagon?
CCSS.MATH.CONTENT.2.G.A.1

Basics on the topic What is a Pentagon?

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Nico and Nia are at the arcade and just found their favorite game, the claw machine! However, this is a special kind of claw machine, it only releases prizes that are shaped like pentagons. They do their best to see where is the pentagon, before they choose prizes with the claw, but they need to learn more about the pentagon meaning in order to claim their prize!

What is a Pentagon?

Before we talk about the pentagon shape, let’s talk about the type of shape a pentagon is. Are pentagon's quadrilaterals? No, a quadrilateral is a shape that has four sides. How many sides does a pentagon have? First, it is important to note that a pentagon the shape, is a polygon. A polygon is a two-dimensional shape that is made of straight lines and is fully closed. What is a pentagon shape? A pentagon is a five-sided polygon.

What is the Shape of the Pentagon?

Pentagons can be defined by three attributes. In order for a shape to be identified as a pentagon, it must have ALL of the defining attributes:

Five straight sides Five corners Fully closed shape

pentagon-five-straight-sides-five-corners-fully-closed-shape-pentagons.svg

Now that we know what polygon has 5 sides, let’s answer some questions about pentagons.

How Many Sides are on a Pentagon?

In other words, a pentagon has how many sides? In order for a shape to be classified as a pentagon it must have five straight sides. However, it’s not just about the pentagon sides, it must have two more attributes as well!

How Many Angles Does a Pentagon Have?

Now that we know the answer to: “how much sides does a pentagon have?”, let’s take a look at the next attribute. A pentagon must also have five corners, which are also referred to as angles. There is one more attribute a shape must have in order to be classified as a pentagon.

What Does a Pentagon Look Like?

Pentagons must also have one last attribute. It must be a fully closed shape. That means all sides must meet to make corners or angles, without leaving any sides open.

Classifying Pentagons

Is this shape a pentagon? Let’s take a look at the attributes.

​​It has five straight sides…

pentagon-five-straight-sides-green-check-five-corners-fully-closed-shape-pentagons.svg

five corners…

pentagon-five-straight-sides-five-corners-green-check-fully-closed-shape-pentagons.svg

and is fully closed!

_pentagon-five-straight-sides-five-corners-fully-closed-shape-green-check-pentagons.svg

This shape is a pentagon!

What's a Pentagon Summary

A pentagon is a five-sided polygon. Pentagons can be defined by three attributes. In order for a shape to be identified as a pentagon, it must have ALL of the defining attributes:

Five straight sides Five corners Fully closed shape

Want to practice identifying pentagons? In this video you can find identifying pentagons examples and on this website there is worksheets along with other activities, and exercises.

Transcript What is a Pentagon?

Nico and Nia are at the arcade and just found their favorite game (...) the claw machine! However, this is a special kind of claw machine (...) it only releases prizes that are shaped like a pentagon. Let's help Nico and Nia identify pentagons in the claw machine by answering the question... "What is a Pentagon?" A pentagon is a special type of shape. Shapes are figures that we can name based on their defining attributes, or traits that make them unique. A POLYGON, is a two-dimensional shape that is made of straight lines and is fully closed. A PENTAGON, is a five-sided polygon. In order for a shape to be identified as a pentagon, it must have ALL of the defining attributes: five straight sides (...) five corners (...) and be fully closed. THIS shape is a pentagon because it has five straight sides (...) five corners (...) and is fully closed. Now that we know the attributes of a pentagon, let's help Nico and Nia identify pentagon prizes in the claw machine! The first prize they've picked is a bubble fidget toy (...) is it a pentagon? Let's check (...) how many sides does it have? (...) It has FOUR straight sides. How many corners? (...) There are FOUR corners. Is it fully closed? (...) Yes, it is a fully closed shape. Even though this shape has one of the defining attributes, it is NOT a pentagon. Remember, in order to be a pentagon, it must have ALL the defining attributes. Next, we see a headband (...) is it a pentagon? (...) It has FIVE sides, (...) and they are all straight. How many corners are there? (...) There are FOUR corners. Is it fully closed? (...) It is NOT a closed shape. The headband does not have ALL the defining attributes, so it is NOT a pentagon. Last, we see a gemstone sticker (...) what a treasure! Is this shape a pentagon? (...) It has five sides, (...) five corners, (...) and is fully closed! It has ALL the defining attributes! This shape IS a pentagon, so Nico and Nia get to keep this prize! Before we see if Nico and Nia will get more prizes, let's summarize. Remember (...), a pentagon is a polygon with five sides. In order for a shape to be identified as a pentagon, it must have ALL of the defining attributes: five straight sides (...) five corners (...) and be fully closed. Oh, the claw machine picked up a soccer ball! Uh oh, I think the claw might be too sharp to hold that... look out Nico and Nia! Phew! I'm glad they are okay! "Yes! Now we get to keep all the toys!" "You're such a gem, Nia."

What is a Pentagon? exercise

Would you like to apply the knowledge you’ve learned? You can review and practice it with the tasks for the video What is a Pentagon?.
  • What are the properties of a pentagon?

    Hints

    Can you count the sides?

    Can you count the vertices?

    Do all of the sides join or are there any gaps?

    Solution

    A pentagon has 5 straight sides.

    A pentagon has 5 vertices.

    A pentagon is a closed shape.

  • Find the pentagons.

    Hints

    Does it have 5 sides and 5 vertices?

    Is it a closed shape?

    There are 4 correct options.

    Solution

    These shapes are pentagons because they:

    • have 5 sides.
    • have 5 vertices.
    • are closed shapes.

  • What could Nico and Nia get?

    Hints

    Which items have 5 sides?

    Which items have 5 vertices?

    There are 4 pentagon shaped items.

    Solution

    Here are the pentagon shaped items highlighted in violet.

    • The diamond sticker
    • The pop it
    • The pencil sticker
    • The piece of candy
    They are all pentagons because:
    • They all have 5 sides.
    • They all have 5 vertices.
    • They are all closed shapes.

  • Which items are pentagons?

    Hints

    Count the number of sides and vertices. How many should there be if it is a pentagon?

    Is it a closed shape?

    Remember, pentagons can face in any direction.

    Solution

    These items are all pentagons because:

    • they all have 5 sides.
    • they all have 5 vertices.
    • they are all closed shapes.
  • How many pentagons can you see here?

    Hints

    Does the shape have 5 sides?

    Does the shape have 5 vertices?

    Here is an example of a pentagon.

    Solution

    There are 4 pentagons in this picture. Here they are highlighted in green.

    They all:

    • have 5 sides.
    • have 5 vertices.
    • are closed shapes.
  • How many pentagons can you see?

    Hints

    How many sides must a shape have to be a pentagon?

    How many vertices must a shape have to be a pentagon?

    All pentagons are:

    • 5 sided shapes
    • shapes with 5 vertices
    • closed shapes
    Solution
    • The house has 4 pentagons.
    • The boat has 3 pentagons.
    • The necklace has 5 pentagons.
    • The sign has 2 pentagons.