Virginia SOL Math / Grade 3 / Measurement & Geometry

3.MG.4

Polygons

What you'll learn

  • Identify and name polygons by their number of sides
  • Classify, compare, and contrast polygons
  • Combine and subdivide polygons to make new shapes

Words to know

Polygon —
a closed shape with straight sides
Side —
one straight edge of a polygon
Vertex —
a corner where two sides meet
Quadrilateral —
a polygon with 4 sides

Why it matters Recognizing shapes helps us describe the world — signs, tiles, windows — and build and design with them.

Worked examples

Model ItI do

Name each polygon by its number of sides.

3 sides is a triangle, 4 sides is a quadrilateral, 5 sides is a pentagon, and 6 sides is a hexagon. Count the sides to name any polygon.

Try It TogetherWe do

Two triangles are put together along one side to form a new shape. How many sides does the new shape have?

Joining two triangles along a full side makes a quadrilateral — a shape with 4 sides.

Now YouYou do

How many sides and vertices does a hexagon have?

Recall what 'hexagon' means. Check your answer in the back.

Practice

Mastered 0 of 11

Warm-up

Ease in with the basics.

  1. 1.How many sides does a triangle have?

  2. 2.What is the name for a 6-sided polygon?

  3. 3.How many vertices does a quadrilateral have?

On Level

The core Quick Check from the book.

  1. 1.How many sides does a pentagon have?

  2. 2.What is the name for a 4-sided polygon?

  3. 3.How many vertices does a triangle have?

  4. 4.Is a circle a polygon? Why or why not?

  5. 5.You cut a square along a diagonal. What two shapes do you get?

Challenge

Stretch your thinking.

  1. 1.Two triangles are joined along one full side to make a new shape. Name the new polygon and tell how many sides it has.

  2. 2.A polygon has one more side than a pentagon. Name it and tell how many vertices it has.

  3. 3.You cut a square straight across from one corner to the opposite corner. Name the two shapes you get.