Area of Rectangles, Triangles and Parallelograms

The areas of rectangles, parallelograms and triangles all come from one idea, base times perpendicular height, halved for a triangle: \(A = bh\) for a parallelogram and \(A = \frac{1}{2}bh\) for a triangle. This NSW Year 8 maths subtopic (NESA outcome MA4‑ARE‑C‑01) builds on the formulas met in Year 7.

You will pick the height that meets the base at a right angle, ignore sloping sides, read a base and height off a number plane, and change lengths to one unit before multiplying. You will work backwards from an area to a missing base or height, find composite areas, see what happens when the base or height changes, and cost the turf for a backyard. It is part of Year 8 Area and Perimeter.