Maths Unit 6 – Area & Perimeter Finding the perimeter and area by counting To find the perimeter of the shape to the right, you count around the outside of the shape. The perimeter of this shape is 26cm. To find the area of the shape to the right, you count the number of squares inside the shape. The area of this shape is 19cm². = 1cm² Working with circles Formulae you need to know to find the area of different shapes The diameter = 2 x radius The radius = ½ of the diameter π = 3.142 Key words and definitions Perimeter – The distance around the outside of a shape Area – Space inside a 2D shape Circumference - The distance around the outside of a circle Diameter – A straight line passing from one side to the other of a circle through the centre Radius – A straight line passing from the centre to the circumference of the circle Parallelogram – A quadrilateral with two pairs of parallel lines Trapezium – A quadrilateral with one pair of parallel lines