P5 · Topic
Area of Triangle
Area = ½ × base × perpendicular height.
Big Idea
Area = ½ × base × perpendicular height.
Key points
- 1Height must be perpendicular to the chosen base.
- 2Any side can be the base — pick the easiest.
- 3Composite figure: split or subtract simple shapes.
- 4Units: cm × cm = cm².
Worked example
- 1Area = ½ × base × height.
- 2Area = ½ × 16 × 9 = 72 cm².
Answer: 72 cm²
GYM Teaching Tip
Draw a small right-angle square on the height so you don't use a slant side.
See the question behind this example
A triangle has base 16 cm and perpendicular height 9 cm. Find its area.