NUMBAT OER - Open Educational Resources

2. Two-dimensional shapes

2.1 Quadrilaterals (shapes with four straight sides) and triangles (shapes with three straight sides)

Shape Perimeter Area
Square
(all sides equal and opposite sides parallel, all angles right angles)
4 x x2

Rectangle
(opposite sides equal and parallel, all angles right angles)

2 (x + y) xy

Parallelogram
(opposite sides equal and parallel, corner angles not right angles)

(see also note below)

2 (x + y) xh

Trapezium
(two opposite sides parallel but unequal)

x + y + a + b h (y + 0.5 (x -y))
Triangle
(three sides: special cases where all sides equal = equilateral; and two sides equal = isosceles)
x + y + z 0.5 hz

Note: a parallelogram where all four sides are equal is called a rhombus