1. Area and Perimeter Review

2. 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.

3. 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)

4. 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

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

6. 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

7. 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

8. 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 =
= 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 = cm2
Divide 2 and 6 by 2
Perimeter = 18 cm Area = 21 cm2

9. 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