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Area and perimeter
Perimeter is the distance around a shape; area is the space inside. Learn the formulae and break harder shapes into simple ones.
Formulae
Compound shapes
Split an L shape or a house shape into rectangles and triangles. Find each area and add.
For perimeter, add every outside edge, working out any missing lengths.
For perimeter, add every outside edge, working out any missing lengths.
Units
Area is in square units: cm2, m2.
Always use the perpendicular height, which meets the base at a right angle.
Always use the perpendicular height, which meets the base at a right angle.
A trapezium has parallel sides 6 cm and 10 cm and height 4 cm. Find its area.
- 12(6 + 10) × 4
- = 12 × 16 × 4
- = 32
Answer: 32 cm2
Rectangle lw, triangle ½bh, parallelogram bh, trapezium ½(a + b)h. Split compound shapes and use perpendicular heights.
The interactive lesson includes the diagrams for this topic.
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