Fields and Fences - Perimeter of Rectangles and Squares

Perimeter is the total length of the boundary of a closed flat shape. Imagine walking along the edge of a field from one corner and continuing until you return to the exact same starting point; the distance you walked is the perimeter.

The units of perimeter are the same as the units of length, such as centimeters ($cm$), meters ($m$), or kilometers ($km$). If you are measuring a small postcard, you use $cm$, but for a large park, you use $m$.

A rectangle has four sides where the opposite sides are equal in length. Visually, this means the top and bottom edges are identical, and the left and right edges are identical. These are called Length ($l$) and Breadth ($b$).

A square is a special type of rectangle where all four sides are of equal length. If you look at a square floor tile, you will notice that every side looks exactly the same because the distance from corner to corner is constant for all four edges.

The perimeter of any polygon is calculated by adding the lengths of all its sides. If a shape has five sides of different lengths, you simply sum them up to find the total boundary length.

In real-world problems, calculating perimeter is often referred to as 'fencing.' For example, if a farmer wants to put a wire fence around a rectangular field to keep cows inside, they need to calculate the perimeter to know how much wire to buy.

To find a missing side of a square when the perimeter is known, you can divide the total perimeter by $4$, because all four sides contribute equally to the total length.