This deep dive covers Why is Triangle Area = ½ × Rectangle? within Area of Rectangles & Triangles for GCSE Mathematics. Revise Area of Rectangles & Triangles in Geometry & Measures for GCSE Mathematics with 12 exam-style questions and 6 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 3 of 8 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Why is Triangle Area = ½ × Rectangle?
1
Draw a rectangle around any triangle
2
The triangle takes up exactly HALF the rectangle
3
So: Triangle = ½ × (base × height) = ½ × Rectangle
Practice questions for Area of Rectangles & Triangles
Which formula gives the area of a rectangle with length l and width w?
Explain why the area formula for a triangle uses the perpendicular height rather than the slant height.
Quick recall flashcards
Triangle Area
Area = ½ × base × perpendicular height (A = ½bh)
Rectangle Area
Area = length × width (A = l × w)