All About Area & Perimeter 2

Definition: The perimeter of a shape of figure is the total length of the edges of that shape or figure : in other words, the total distance around the shape. The perimeter of a rectangle = sum of all four sides =l+l+b+b =( 2 x length ) + ( 2 x breadth) = 2 (l + b)

The perimeter of a triangle = sum of lengths of its 3 sides = AB + BC + CA

The perimeter of an octagon = sum of lengths of 8 sides = a + b+ c + d + e + f + g + h If it is a regular polygon, all the sides will be the same length then = 8 x a = 8a

Area is the measure of the actual surface of an object / figure. In two dimensional shapes, the area would be the space contained within the edges of the shape We use the area of a 1cm x 1cm square which is called one square centimeter or 1cm². The larger the area we measure, the larger the unit: 1m² or 1km² To find the area of a shape or figure we usually use multiplication.

Area of a rectangle = length x breath =lxb = lb

Area of a square = length x length = l²

The unit area is always a length unit squared examples: cm², m², km², miles² What is the area of the following shape? A=lxb = 8cm x 6cm = 48cm²

Find the area of a brick path 2m wide around a rectangular swimming pool 12m by 7m Total area around path and pool A=lxb = 16m x 11m = 176m² Area of pool = l x b = 12m x 7m = 84m² Area of path = 176m² - 84m² = 92m²

From rectangle ABCD, we can see that if we divide it in half from vertex to vertex, we form two right-angled triangles. Therefore the area of a right-angled triangle would be half the area of a rectangle. Area = ½ (l x b) This formula for the area of a triangle applies to all triangles. A = ½ (h x b)

This triangle is also half a rectangle with its height equal to the rectangle's breadth and its base to the equal rectangle's length. A = ½ ( base x height ) = ½ (7cm x 4cm) = ½ (28cm²) = 14cm²

Find: a) the perimeter of the figures below, b) the areas of figures 1, 2, 3 , 4 and 8, c) the unshaded areas of the figures 5, 6, 7 and 9