Measurement - Introduction to Perimeter and Area

Perimeter is the total distance around the outside edge of a 2D shape. Imagine a tiny ant walking along the boundary lines of a shape until it returns to the starting point; the total distance the ant traveled is the perimeter. It is measured in linear units like $cm$, $m$, or $inches$.

Area is the amount of flat space or surface covered inside a 2D shape. Imagine you are tiling a floor or covering a table with stickers; the number of square units needed to cover the entire surface without any gaps or overlaps is the area. It is measured in square units like $cm^{2}$ or $m^{2}$.

Measuring Area with Grids involves counting the number of identical square units inside a shape. Visualise a rectangle drawn on grid paper; if you count $12$ small squares inside the boundary, the area is $12$ square units. This is a foundational way to understand area before using formulas.

The Perimeter of any polygon is calculated by adding the lengths of all its sides together. For a rectangle, you can see two pairs of equal sides. If the sides are labeled $a, b, c, d$, the perimeter is $a + b + c + d$.

A Rectangle has four sides where the opposite sides are equal in length and all corners are right angles. To find its perimeter, you add the length and width and then double the sum. To find its area, you multiply the length by the width.

A Square is a special type of rectangle where all four sides are exactly the same length. Visualise a box where every edge is identical. Because all sides are equal, you can find the perimeter by multiplying one side by $4$, and the area by multiplying the side by itself.

Units of Measurement are different for perimeter and area. Perimeter uses one-dimensional units like centimeters ($cm$) because it measures a line. Area uses two-dimensional units like square centimeters ($cm^{2}$) because it measures a surface.