Perimeter and area · Grade 8
In Grade 8 you learn: units of area.
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
- Triangle: area = ½ × base × perpendicular height.
- Parallelogram: area = base × perpendicular height.
- Trapezium: area = ½ × (a + b) × h, where a and b are the parallel sides.
Worked examples
Example 1
A triangle has a base of 10 cm and a perpendicular height of 7 cm. Find its area.
Answer: 35 cm²
Example 2
A trapezium has parallel sides of 6 cm and 10 cm and a height of 5 cm. Find its area.
Answer: 40 cm²