Ctrl+k

Describe shapes by sides

A shape can be described by counting its straight sides, which are line segments joined at corners: triangles have 3, quadrilaterals have 4, pentagons have 5, and hexagons have 6. The number of sides remains the same when a shape is rotated, resized, or shown in a different orientation; curved boundaries are not counted as straight sides. Formal angle measurement and classification of more complex polygons are beyond this understanding.

Detailed Explanation: Describe shapes by sides

Look at the outside edge of the shape.

  1. Count only the straight sides.
  2. Touch each side as you count it once.
  3. Match the number of sides to the shape name:
    • 33 sides: triangle
    • 44 sides: quadrilateral
    • 55 sides: pentagon
    • 66 sides: hexagon

Example

A shape is turned sideways. Starting at the top, count its straight sides:

  • 1 side
  • 2 sides
  • 3 sides
  • 4 sides
  • 5 sides

It has 55 straight sides, so it is a pentagon.

Turning or resizing the shape does not change the number of sides. If part of the edge is curved, do not count the curved part as a straight side.

Learn by doing: Describe shapes by sides

Click a topic below to practice the foundational skills you'll need, learn the steps, or master this skill

    Practice with unlimited practice problems

    Count Sides on 2D Shapes

      ?