In geometry, the perimeter of a shape is defined as the total length of its boundary. The perimeter of a shape is determined by adding the length of all the sides and edges enclosing the shape. It is measured in linear units of measurement like centimeters, meters, inches, or feet. Let’s try to calculate the perimeter of the
following shape: Perimeter of a shape = Sum of all its sides, Therefore, Perimeter of the given shape = 6 cm + 5 cm + 5 cm + 4 cm + 3 cm = 23 cm. We often use the concept of perimeter in real life. For example, when putting up Christmas lights around the house or when we want to put a fence around the backyard, we find its perimeter to know the length of wire we will need. We know that the length of each side of a regular polygon is the same. For example, look at the given regular pentagon. The perimeter of the given regular
pentagon can be calculated as follows: Number of sides = 5 Therefore, Perimeter = number of sides ✕ length of one side = 5 ✕ 4 = 20 cm The given table summarizes the formulas to find the perimeter of some regular polygons: Since the sides of an irregular polygon may not all be the same in length, we use the general formula to find the perimeter of an irregular
shape. Example 1: What is the perimeter of the given figure? Solution: We know that the perimeter of a triangle is given by Perimeter = a + b + c, Where a, b, c = length of three sides. Therefore, For the given triangle,What is Perimeter?
Real – World Applications
Perimeter of a Regular Shape
Therefore,
Perimeter of regular polygon = sum of all its sides = number of sides ✕ length of one side.
Length of one side = 4 cmPerimeter of An Irregular Shape
Therefore,
Perimeter of irregular polygon = sum of all sides.
Solved Examples
Perimeter = 5 cm + 4 cm + 3 cm = 12 cm
Example 2: Calculate the perimeter of the following figure.
Solution:
The given shape is an irregular pentagon.
The perimeter of this pentagon will be given by the sum of all its sides.
Perimeter = 2 cm + 3 cm + 3 cm + 4 cm + 5 cm = 18 cm
Example 3: What will be the perimeter of a rectangle with length 12 cm and breadth 5 cm?
Solution:
We know that the perimeter of a rectangle is given by
Perimeter = 2 ✕ (l + b),
Where l = length of the given rectangle, b = breadth of the given rectangle.
For the given rectangle, l = 12 cm, b = 5 cm.
Therefore, perimeter of given rectangle = 2 ✕ (12 + 5) = 2 ✕ 17 = 34 cm
Practice Problems
120 cm
45 cm
160 cm
180 cm
Correct answer is: 160 cm
Perimeter of the given square = 4 ✕ 40 = 160 cm
100 cm
88 cm
60 cm
85 cm
Correct answer is: 88 cm
Perimeter of the given rectangle = 2 ✕ (30 + 14) = 2 ✕ 44 = 88 cm
44.96 cm
38.96 cm
54.06 cm
43.96 cm
Correct answer is: 43.96 cm
Perimeter of given circle = 2 ✕ 3.14 ✕ 7 = 43.96 cm
15 cm
20 cm
28 cm
24 cm
Correct answer is: 20 cm
Perimeter of irregular polygon = sum of all sides
Perimeter of given irregular polygon = 6 cm +
4 cm + 2 cm + 2 cm + 4 cm + 2 cm = 20 cm
Frequently Asked Questions
How many sides are required to determine the perimeter of a regular heptagon?
We only require the length of one side to determine the perimeter of any geometric figure with sides of equal length, such as a regular heptagon. The area of a heptagon = 7 ✕ a, where a is the side length.
What is the difference between the perimeter and area of a 2-D shape?
Perimeter measures the length of the boundary of the shape. It is given by the sum of all sides of the shape. It is one-dimensional and expressed in linear units.
Area, on the other hand, measures the space occupied by the shape. It is two-dimensional and is expressed in square units.
How can we find the perimeter of a polygon?
The most general way to find the perimeter of any polygon is to find the sum of all its sides. However, another way of finding the perimeter of a regular polygon is to multiply the number of its sides by the side length.