3rd Grade - Classify Polygons Like Pentagons

Shapes and Geometry
Classify Polygons Like Pentagons
Be able to identify and classify multiple-sided figures. (Multiple-sided figures are called polygon and each has a specific name depending on its number of sides.)
Measurement and Geometry: Classify polygons The ability to know that shapes with the same number of sides and corners are called polygons. The ability to label different shapes depending on the number of sides each has.

Sample Problems


Define an open and closed figure. (an open figure has lines that do not meet; whereas in a closed figure every line meets another line)

Define a side and a corner. (a side is a line segment that is part of a closed figure and a corner is the point where two sides meet). Define polygon (A figure with the same number of sides as corners).


A polygon has straight-line segments.

Each segment touches two other segments at each of its endpoints.

Polygons are closed figures.


Polygons are classified as the number of sides that they have.

3-Triangle 8-Octogon

4-Quadrilateral 9-Nonagon

5-Pentagon 10-Decagon




Regular polygons have sides that are all the same length and angles that are the same size. (e.g., squares, triangles, hexagons, pentagons)


Some polygons have line symmetry meaning that you can fold it in half and the two halves will match exactly. The “folding line” is called the line of symmetry.

Learning Tips


Draw several different types of figures and have the child indicate whether they are open or closed figures. Have the child name each and give an attribute (square, circle, rectangle, triangle). A circle is not a polygon because it does not have straight sides.


Use a geoboard (square board with pegs sticking up in rows and columns—uses rubber bands to stretch across the pegs to make figures) to have children practice making polygons. Children can be given a number of sides and corners and asked to make the figure and then name it.


Children can cut a square out of paper and then slowly cut off the corners to make other polygons. He/she can name and count the corners and sides of the new figure.


Ask the child to find and name polygons in his/her environment. For example, children can look for shapes when driving along in the car—stop signs and other road signs, shapes of buildings, etc. Talk about the idea that many types of polygons come together to make different shapes.


Make symmetrical greeting cards by asking the child to draw simple hearts and flowers or triangles and circles. Half of the shape can be drawn on a folded piece of paper and then cut out or the child can fold the shape in half after cutting it out and make sure both halves match (trim as necessary). The child can then decorate and make greeting cards for friends and family. Draw the child’s attention to symmetry and the line of symmetry.

Extra Help Problems


Is this a polygon: (Show a picture of a diamond.) Yes or No? (Yes)


Is this a polygon: (Show a picture of an open figure.) Yes or No? (No)


Is a circle a polygon? Why or why not? (No, it has no straight line segments)


Is a “c” shaped object a polygon? (No, it’s an open figure. Polygons have to be closed.)


What is the line called when you fold a figure in half and one half matches the other half exactly? (line of symmetry)


Look around, inside or outside, and name three polygons that you see. Write down the names and write down what the objects are used for.


Draw a triangle. How many sides and corners does it have? (3)


Draw a octogon. How many sides and corners does it have? (8)


Draw a quadrilateral. How many sides and corners does it have? (4)


Draw a pentagon. How many sides and corners does it have? (5)


Draw a decagon. How many sides and corners does it have? (10)


Draw a septagon. How many sides and corners does it have? (7)


Draw a nonagon. How many sides and corners does it have? (9)


Draw a hexagon. How many sides and corners does it have? (6)


For additional extra help problems, see the attached PDF.


Related Games


Copyright ©2009 Big Purple Hippos, LLC