Perimeter is the distance all the way round a shape. Area is how much flat space it covers. Symmetry is about folding a shape in half so both sides match exactly. Three different ideas, three simple rules.
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The perimeter of ANY shape is just the total length of all its sides added together.
Special formulas for two common shapes
Rectangle
Perimeter = 2 × (length + breadth)
Square
Perimeter = 4 × side
For an irregular shape (like a triangle with 3 different sides, or an odd-shaped garden), there is no shortcut — just add up all the side lengths.
Area tells you how much flat surface a shape covers, measured in square units.
Don't mix up perimeter and area! Perimeter uses ADDITION (or × for regular shapes) and is measured in plain units (cm, m). Area uses MULTIPLICATION and is measured in square units (cm², m²).
A shape has a line of symmetry if you can fold it along that line and both halves match up exactly.
| Shape | Lines of symmetry |
|---|---|
| Square | 4 |
| Rectangle | 2 |
| Equilateral triangle | 3 |
| Isosceles triangle | 1 |
| Regular pentagon | 5 |
| Regular hexagon | 6 |
| Circle | infinite |
Pattern to notice: a regular shape (all sides and angles equal) has as many lines of symmetry as it has sides!
12 IMO-style questions on perimeter, area and symmetry. 🍀
