9. The longer side of a picture frame is $5 / 4$ of the shorter side. The frame has the same thickness on all four sides. In the picture inside the frame (represented by a gray rectangle), the longer side measures $32 \mathrm{~cm}$ and the shorter side 24. By how many $\mathrm{cm}^{2}$ is the area of the rectangle delimited by the outer edge of the frame?
(A) 1440
(B) 1200
(C) 1280
(D) 1600
(E) 1500

![](https://cdn.mathpix.com/cropped/2024_04_17_94b06074249d24c20b4bg-1.jpg?height=231&width=287&top_left_y=1641&top_left_x=2445)
(9) The correct answer is $(C)$.

Let $\Delta$ be the thickness of the frame. By hypothesis, we have $32+2 \Delta=\frac{5}{4}(24+2 \Delta)$, from which we deduce $\Delta=4$. The area of the rectangle delimited by the outer edge of the frame is $(32+8) \cdot(24+8)=1280 \mathrm{~cm}^{2}$. Question proposed by Paolo Negrini.