Analysis process: Because the shadow part is an irregular figure, we can use two square areas-blank area = shadow area. As can be seen from the figure, the blank part in the big square is a triangle, and both the bottom and the height are known, so the area of the first blank part is 5×5÷2= 12.5 (the bottom is multiplied by the height ÷2). The area of the other blank part is the side length of the big square+the side length of the small square, 8cm and 3cm high. So the area of the second blank part is 3×8÷2= 12, so the area of the shadow part is 5× 5+3-12.5-12 = 9.5.

Formula: 5×5÷2= 12.5cm?

3×8÷2= 12cm？

5×5+3×3- 12.5- 12 = 9.5cm？

A: The shadow area is 9.5cm?

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