Finding the Area of a Polygon Using Smaller Rectangles

This lesson teaches how to find the area of a polygon by dividing it into smaller rectangles. It begins with a review of basic area concepts, emphasizing the importance of multiplying length by width for rectangles. The lesson then addresses common mistakes, such as incorrectly multiplying side lengths of irregular shapes. It demonstrates how to break down complex polygons into smaller, manageable rectangles, calculate their individual areas, and sum them to find the total area. The lesson concludes with a summary of these techniques.

What is a common mistake when calculating the area of a polygon?

• Counting each square tile individually

• Dividing the perimeter by two

• Adding all the side lengths

• Multiplying the length and width of any two sides

How can you find the area of a complex polygon without counting each square tile?

• By multiplying the longest side by the shortest side

• By breaking it into smaller rectangles and adding their areas

• By estimating the area visually

• By measuring the perimeter and dividing by four

In the first example, what is the area of the black rectangle?

• 12 square units

• 9 square units

• 15 square units

• 10 square units

What is the total area of the polygon in the first example?

• 18 square units

• 21 square units

• 19 square units

• 20 square units

In the second example, what is the area of the blue rectangle?

• 10 square units

• 4 square units

• 6 square units

• 8 square units

What is the total area of the polygon in the second example?

• 22 square units

• 24 square units

• 26 square units

• 28 square units

What is the key takeaway from this lesson on finding the area of polygons?

• Use the perimeter to find the area

• Always count each square tile individually

• Break the polygon into smaller rectangles and sum their areas

• Multiply the longest and shortest sides