**Perimeter** refers to the entire length of a figure or the distance around it. If the figure is a circle, the length is referred to as the **circumference.** Such lengths are always measured in linear units such as inches, feet, and centimeters. **Area** refers to the size of the interior of a planar (flat) figure. Area is always measured in square units such as square inches (in^{2}), square feet (ft^{2}), and square centimeters (cm^{2}), or in special units such as acres or hectares.

For all polygons, you find perimeter by adding together the lengths of all the sides. In this article, *P* is used to stand for *perimeter*, and *A* is used to stand for *area.*

Finding the perimeter

Figures 5.1(a) and 5.1(b) show perimeter formulas for squares and rectangles.

**Figure 1 **Perimeter of a square and perimeter of a rectangle.

Area formulas for squares and rectangles are formed by simply multiplying any pair of consecutive sides together. Refer to Figures 5.1(a) and 5.1(b).

**Example 1:** Find the perimeter and area of Figure 2.

**Figure 2 **Finding the perimeter and area of a square.

This is a square.

**Example 2:** Find the perimeter and area of Figure 3.

**Figure 3 **Finding the perimeter and area of a rectangle.

This is a rectangle.

**Example 3:** If the perimeter of a square is 36 ft, find its area.

The area of the square would be 81 square feet.

**Example 4:** If a rectangle with length 9 in has an area of 36 in ^{2}, find its perimeter.

The perimeter of the rectangle would be 26 inches.