Perimeter & Area
Year 7 📐 Geometry & Measures Calculate perimeter and area of rectangles, triangles and compound shapes.
📏 Perimeter
The perimeter is the total distance around the outside of a shape. Add up all the side lengths.
⚡ Rectangle Perimeter
$$P = 2(l + w)$$Example: A rectangle with length 8 cm and width 5 cm: $P = 2(8 + 5) = 2 \times 13 = 26$ cm
📐 Area of Common Shapes
Area measures the space inside a 2D shape. Units are always squared (cm², m², etc).
⚡ Key Area Formulas
$$\text{Rectangle: } A = lw$$$$\text{Triangle: } A = \frac{1}{2}bh$$$$\text{Parallelogram: } A = bh$$$$\text{Trapezium: } A = \frac{1}{2}(a+b)h$$Example: Triangle with base 10 cm and height 6 cm: $A = \frac{1}{2} \times 10 \times 6 = 30$ cm²
🔵 Area and Circumference of a Circle
Circles use the special number $\pi \approx 3.14159\ldots$
⚡ Circle Formulas
$$\text{Circumference: } C = 2\pi r = \pi d$$$$\text{Area: } A = \pi r^2$$Example: Circle with radius 7 cm: $A = \pi \times 49 = 49\pi \approx 153.9$ cm²
Leave answers in terms of $\pi$ unless asked for a decimal approximation.
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Interactive Demonstration — Perimeter & Area
📐 Area & Perimeter Tool