Understanding Perimeter

We all know that there are many classifications of Polygons, and one of those is QUADRILATERALS, a 4 sided polygon.  There are many examples of quadrilaterals, but most common quadrilaterals are SQUARE, RECTANGLE and PARALLELOGRAM. In this topic, we will be discussing on how to calculate the perimeter of a square, rectangle and parallelogram.

Perimeter is the distance around a two-dimensional shape.  Two-dimensional shape, are shapes with two dimensions such as width and height, and perfect example of two dimensional shapes are square, rectangle and parallelogram.

Below is a short description on understanding perimeter of Square, Rectangle and Parallelogram

Let’s first understand the perimeter of a square. As we all know, a square is a quadrilateral with 4 equal sides. Meaning, side a = side b = side c = side d.  For better understanding, see illustration below

How to Calculate the Perimeter of a Square

Perimeter of a Square

So to compute for the perimeter of a square, we do follow this simple formula:

P = a + b + c + d

Where: P = Perimeter

  • A = Side A
  • B = Side B
  • C = Side C
  • D = Side D

Or P = 4.S

Where: P = Perimeter     S = Sides

Since a square has a uniform dimensions of the sides.

Let’s take this as an example:

Perimeter of a Square

Shown is a square with a side dimension of 5 inches.  Find the perimeter.

Solution:

P = a +b +c + d           OR      P = 4.S

P = 5 + 5 + 5 +5                      P = 4 x 5

P = 20 inches                      P = 20 inches

 Any solution or formula you used will still result to the same answer.

How to Calculate the Perimeter of a Rectangle

And now, I will let you know how to compute for the perimeter of a rectangle.  Though square and rectangle are both quadrilaterals, but still a RECTANGLE has different sides, wherein Base 1 = Base 2, while Height 1 = Height 2.

See illustration below:

So to compute for the perimeter of a rectangle, we will be using this formula:

P = 2.B + 2.H

Where:

  • P = Perimeter
  • B = Base 1 and 2
  • H = Height 1 and 2
Perimeter of a Rectangle

Using the formula, we can identify that B = 25 cm. and H = 15 cm. So now were ready to solve

P = 2.B + 2.H

P = 2 x 25 cm + 2 x 15 cm

P = 50 cm + 30 cm

P = 80 cm.

So the perimeter is equal to 80 cm.

Perimeter of a Rectangle

Hint:

In some Math questions, the perimeter and either the base or height is given.  In this case, we could still use the same formula, but just equate this to the needed requirement

P = 2.B + 2.H

P = 2 x 25 cm + 2 x 15 cm

P = 50 cm + 30 cm

P = 80 cm.

So the perimeter is equal to 80 cm.

Hint:

In some Math questions, the perimeter and either the base or height is given.  In this case, we could still use the same formula, but just equate this to the needed requirement

 

How to Calculate the Perimeter of a Parallelogram

So now, we will move on to computing the Perimeter of a Parallelogram.  Just like a rectangle, a parallelogram is a quadrilateral with two different sides; the only difference is that a parallelogram has two parallel sides, to further understand see illustration below:

Perimeter of a Parallelogram

As shown in the illustration, there are three essential parts of a parallelogram:

  • Side a, which is parallel to the opposite side
  • Side b, which is parallel to the opposite side
  • And h, which is the horizontal height

Since the sides of a parallelogram are parallel to each other, the formula to be used in computing for its perimeter is:

P = 2 (a +b)      where:

  • P= Perimeter,
  • a = side a, and
  • b = side b.
Parallelogram

Lets try one example

Since b = 14 inches, a = 10 inches.  We can now compute for the perimeter

Solution:

P = 2 (a +b)

P = 2 (10 + 14)

P = 2 (24)

P = 48 inches

Test your knowledge on Perimeters

Based on the below rectangle answer the next 3 questions

Rectangle Maths Year 6

 

 

 

 

 

[watupro 156]

 

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