Finding the Perimeters of Shapes Made Up of Rectangles and Squares Some figures are a combination of rectangles and squares. Think of the floor plan of your house. Assuming you don't have any turrets or other nonrectangular areas, it's likely that you could sketch the floor plan using only rectangles and squares. To find the perimeter of such a figure, look only at the outside edges. 

Example: Find the cost of weather stripping needed to seal the edges of the boat hatch pictured at right. Weather stripping costs $0.12 per foot. Recall that perimeter is the sum of all the outside edges: P = 10 ft + 25 ft + 5 ft + 10 ft + 5 ft + 15 ft = 70 ft The perimeter of the hatch is 70 feet. The dimensions highlighted in red were not explicitly stated on the diagram, but enough information was provided to determine these values. Take a moment now to be sure you understand where the additional 10 feet and 5 feet came from. Finally, calculate the cost of the required weather stripping. 70 ft X ($0.12/ft) = $8.40 

