Main content

## 4th grade (Eureka Math/EngageNY)

### Course: 4th grade (Eureka Math/EngageNY) > Unit 4

Lesson 4: Topic D: Two-dimensional figures and symmetry- Intro to reflective symmetry
- Identifying symmetrical figures
- Identify line symmetry
- Symmetry review
- Classifying triangles by angles
- Classifying triangles
- Worked example: Classifying triangles
- Classify triangles by angles
- Classify triangles by side lengths
- Types of triangles review
- Classifying shapes by line and angles types
- Quadrilateral properties
- Classifying shapes by lines and angles
- Classify shapes by line and angle types
- Polygons review
- Classify triangles by both sides and angles

© 2023 Khan AcademyTerms of usePrivacy PolicyCookie Notice

# Polygons review

CCSS.Math:

Review the term polygon and name polygons with up to 8 sides. Then, try some practice problems.

## What is a polygon?

A polygon is a closed figure with at least 3 straight sides.

## Practice set 1

*Want to learn more about recognizing shapes? Check out this video.*

## Identifying polygons

Polygons can be named by their number of sides.

Number of sides | Name |
---|---|

3 | Triangle |

4 | Quadrilateral |

5 | Pentagon |

6 | Hexagon |

7 | Heptagon |

8 | Octagon |

### Practice set 2

*Want to try more problems like this? Check out this exercise*

## Want to join the conversation?

- I have learned about Geometry basic here, then I want to curious how many polygons or shape in the world at all ? only till to 8 (Octagon) or is there more polygons ?(48 votes)
- There are many more! 9 sides? Nonagon, 10 sides? Decagon. And so on and so on until there are so many sides you could hardly tell the difference between them and circles.(50 votes)

- What is a 24-sided shape called?(20 votes)
- A icositetragon

An icosogon is 20 sides, and tetra means 4.

Put them together and you get 24(29 votes)

- What's a polygon(18 votes)
- A polygon is made of any three straight sides with the lines all connected to each other, as well as not overlapping and meeting at the ends of the lines.(18 votes)

- what would be a 20 side shape be called(12 votes)
- A 20-sided shape is known as an icosahedron.(12 votes)

- What is the difference Between a Circle, Ellipse And an oval .(7 votes)
- The difference is; with a circle the diameter IS THE SAME all the way around, but with a ellipse the diameter CAN CHANGE as you go around, so a circle is a ellipse but an ellipse is not always a circle. Hope this helps!(23 votes)

- What are the names for the polygons above octagon?(10 votes)
- 9--Nonagon

10--Decagon

11--Hendecagon

12--Dodecagon(14 votes)

- why does every shape have gon at the end, like hexagon or a pentagon ect.(11 votes)
- -Gon is a suffix for a shape that has a specific number of angles.(12 votes)

- What is a 30 sided shape called ?(10 votes)
- Thank you, I never knew that a 30 sided shape was called a triacontagon.(3 votes)

- Who invented the word polygon?(7 votes)
- The Greeks invented the word "polygon" probably used by the Greeks well before Euclid wrote one of the primary books on geometry around 300 B.C.

"polygon" has been used in English since around 1560

The word comes from two parts:

"poly-" = many

"-gon" = angle (or knee)(11 votes)

- Actually does anyone know the name of a 20-sided shape?(6 votes)