Areas of Polygons for 7th Grade

In fact, a polygon is any geometric shape made up of sides. In other words, under the umbrella of polygons fall the square, rectangle, parallelogram, trapezoid, and more.

For example, a triangle has 3 sides, every quadrilateral has 4 sides, and so on.

We have already learned to calculate the areas of standard polygons. There are also non-standard polygons, for which there is no specific formula. However, their area can be calculated using two methods:

• We can divide the area of the required polygon into several areas of polygons that we are familiar with, calculate the areas separately, and then add them together to get the final area.
• We can try to "complete" the area of the required polygon into another polygon whose area we know how to calculate, and subtract the area we added. This way, we can get the area of the original polygon.

Example

Let's demonstrate this using a simple exercise:

Here is a drawing of a polygon.

We need to calculate its area. From the start, we can see that this is not a standard polygon, so we will use the first method to calculate its area. We will divide the polygon as shown in the drawing, and we will get two rectangles.

According to the data shown in the drawing, in the rectangle on the right side we get side lengths of 3 and 6, therefore the area of the rectangle will be 18 (multiplication of the two values). In the rectangle on the left side we get side lengths of 4 and 7, therefore the area of the rectangle will be 28 (multiplication of the two values). Thus, the total area of the polygon will be the sum of the two areas we calculated separately, meaning, 18+28=46.