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Door 14 · Grade 4

📐 2D Shapes & Symmetry

A polygon is a closed shape with straight sides

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Polygons — Sides & Corners

A polygon is a closed shape made of straight sides. We name polygons by their number of sides:
Triangle3 sidesQuadrilateral4 sides (square, rectangle…)Pentagon5 sidesHexagon6 sidesA polygon has the same number of corners (vertices) as sides.

Worked example

Problem: How many sides does a pentagon have?

  1. 5 sides.

Answer: 5 sides.

Lines of Symmetry

A shape has a line of symmetry if you can fold it so the two halves match exactly. Some shapes have more than one line of symmetry.
• A square has 4 lines of symmetry.
• A rectangle has 2.
• A circle has endless lines of symmetry.
• A scalene triangle has none.