11 Perimeter
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What does the word perimeter refer to? What if someone asked you to walk the perimeter of a baseball field? What does that mean?
Perimeter: A perimeter is a path that surrounds a two-dimensional object. The word comes from the Greek peri (around) and metre (measure). The term may be used either for the path or its length – it can be thought of as the length of an outline of a shape. The perimeter of a circle is called its circumference.
If you were to walk the perimeter of a baseball field you would walk around the outer edges of the field and calculate the length. If you wanted to find the perimeter of anything it would basically be like walking around the outer edge of it. Obviously we can’t do that for smaller shapes or objects but you get the idea.
When calculating perimeter the answer will always be a linear (or one dimensional) measurement such as feet, inches, metres or centimetres.
Why would perimeter be important to us in the construction world?
Let’s say you are a carpenter and you want to put baseboard in a room. Calculating how much baseboard you need around the walls involves calculating the perimeter of the room. This would also be true for plumbers if they are putting perimeter drain around a house. Perimeter can be used in many different areas of the construction world.
The Perimeter of a Square and a Rectangle
A square and a rectangle are both similar in that they have four sides. Another characteristic that is common to both is each has four right angles. A right angle is an angle of 90 degrees.
In a square, all four sides are equal while in a rectangle the opposite sides are equal but not the adjacent sides. Calculating the perimeter of a square and a rectangle is very similar. First we’ll define what each side is called.
The square is straight forward as the length of each of the sides is the same, and the name of each side is simply “SIDE.” In a rectangle, the long side of the rectangle is referred to as the “LENGTH” while the shorter side is referred to as the “WIDTH.”
Before I go through calculating perimeter of a square and rectangle, take a guess at what the formula might be.
If we go back to our definition and say that the perimeter is the length that surrounds a two dimensional object, then the perimeter of both would be the length of the four sides combined.
[latex]\Large \begin{array}{ll} \textbf{Square:} & \text{Perimeter}= \text{ side}+ \text{ side} + \text{ side} + \text{ side}\\ \textbf{Rectangle:} & \text{Perimeter} = \text{length} + \text{width} + \text{width} + \text{length}\end{array}[/latex]
Would there be any other way to express the two formulas?
Take a guess.
[latex]\Large \begin{array}{ll} \textbf{Square:} & \text{Perimeter}= \text{ side} \times 4 \\ \textbf{Rectangle:} & \text{Perimeter} = (\text{length}\times 2)+(\text{width} \times 2) \end{array}[/latex]
Both versions of each formula are correct and you can