Calculating Area by Decomposing Irregular Shapes

The Organic Chemistry Tutor

This educational video provides a step-by-step tutorial on how to calculate the area (square footage) of an irregular, composite polygon. The instructor uses a clear, high-contrast digital whiteboard to demonstrate the concept of decomposing a complex shape into simpler, manageable rectangles. The lesson begins with a review of the basic area formula for a rectangle before diving into a complex problem involving missing side lengths and multiple subsections. The core theme is the strategy of decomposition—breaking a difficult problem into smaller, solvable parts. The video covers identifying distinct rectangular sections within an irregular shape, deducing missing side lengths using addition and subtraction of parallel sides, and calculating individual areas. It concludes by summing these partial areas to find the total square footage, reinforcing the additive property of area. This resource is highly valuable for upper elementary and middle school mathematics classrooms. It addresses the common student struggle of finding derived dimensions (missing side lengths) on composite figures. Teachers can use this video to model problem-solving strategies for geometry standards related to area, or as a flipped classroom resource for students to review the mechanics of decomposition and area calculation at their own pace.