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Describe shapes by sides and vertices

A shape is described by identifying its straight sides and vertices, or corners, and counting how many of each it has; for common polygons, the number of sides matches the number of vertices (for example, triangles have 3, quadrilaterals 4, pentagons 5, and hexagons 6). This understanding applies regardless of a shape’s size, orientation, or appearance and does not include angle measurement or advanced polygon classification.

Detailed Explanation: Describe shapes by sides and vertices

To describe a shape, count its:

  • Straight sides: the line segments around the shape.
  • Vertices: the corners where two sides meet.

Start at one side and count all the way around the shape. Count each side and each corner once.

Example: Imagine a shape with 5 straight sides.

  1. Start at the top corner.
  2. Trace around the shape, counting each straight side:
    (1,2,3,4,5)(1, 2, 3, 4, 5).
  3. Count the corners where the sides meet:
    (1,2,3,4,5)(1, 2, 3, 4, 5).

The shape has 5 sides and 5 vertices. It is called a pentagon.

A shape’s size or direction does not change the number of sides or vertices.

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Count Sides and Vertices on 2D Shapes


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