Perimeter and area · Grade 9
In Grade 9 you learn: sectors and composite shapes.
Perimeter is the distance all the way round a shape; area is the amount of flat space it covers, measured in square units. Knowing the area formulas for rectangles, triangles, parallelograms and trapeziums lets you work out compound shapes too.
Key facts
- Trapezium: area = ½ × (a + b) × h, where a and b are the parallel sides.
Worked examples
Example 1
A trapezium has parallel sides of 6 cm and 10 cm and a height of 5 cm. Find its area.
Answer: 40 cm²