Area and Perimeter Review

Perimeter When we go around the boundary of the closed figure, the distance covered by us is called the perimeter. Formulas for finding perimeter of a shape: Perimeter of a rectangle = 2 x (length) + 2 x (breadth) = 2 x [length + breadth] = 2 x (l + b) units.

Perimeter of a square = 4 x length of its side = 4 x side = 4 x a units Perimeter of a triangle = Sum of the sides of the triangle = a + b + c units (Perimeter is adding sides outside, should not consider “d” while adding as “d” is inside the triangle)

Area The surface enclosed by a closed figure is called its area. Area of the rectangle = length × breadth = l × b sq. units Area of the square = side × side = a × a sq. units

Area of the triangle = x base x height sq units Base is the side that is perpendicular to the height

Example 1: Find the area and the perimeter of a rectangular field of length 8m and breadth 11 m. Solution: Given: Length = 8 m and Breadth = 11 m To Find: Area and perimeter of a rectangular field Perimeter of the rectangle = 2 x [length + breadth] = 2 x [8 + 11] = 2 x 19 = 38 m Area of the rectangle = length x breadth = 8 x 11 = 88 m2 Ans : Perimeter = 38 m Area = 88 m2

Example 2: Find the area and the perimeter of a square whose side length is 12m. Solution: Given: side = 12m To Find: Area and perimeter of a square Perimeter of a square = 4 x side = 4 x 12 = 48 m Area of a square = side x side = 12m x 12m = 144 m2 Ans : Perimeter = 48 m Area = 144 m2

Example 3: Find the area and the perimeter of the following triangle Solution: Given: Three sides of a triangle AB = 4 cm, AC = 8 cm and BC = 6cm To Find: Area and perimeter of a triangle Perimeter of a triangle = 4 + 6 + 8 = 18 cm (To calculate the perimeter of a triangle, you will need to add the sides outside. should not take 7 as 7 is inside the triangles) AD is perpendicular to BC ∴ Height (AD) = 7cm Base (BC) = 6cm Area of a Triangle = 7 cm 4 cm 6 cm 8 cm A B C D x base x height 3 = x 6 x 7 = 3 x 7 = 21 cm2 Divide 2 and 6 by 2 Perimeter = 18 cm Area = 21 cm2

Try these Find the perimeter of a triangle whose sides are 12m, 15m and 8m Find the area of square whose side is 22m Find the area of Rectangle whose length = 8 cm and breadth = 15 cm