To find the surface area that needs to be decorated (the front, two sides, and top of the box), we can calculate it as follows:
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Dimensions of the box:
- Length (L) = 27 cm
- Width (W) = 20 cm
- Height (H) = 20 cm
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Surface area to be decorated:
- Front face: Length × Height = \( 27 \text{ cm} \times 20 \text{ cm} = 540 \text{ cm}^2 \)
- Top face: Length × Width = \( 27 \text{ cm} \times 20 \text{ cm} = 540 \text{ cm}^2 \)
- Two side faces: Width × Height for each side = \( 20 \text{ cm} \times 20 \text{ cm} = 400 \text{ cm}^2 \) (for one side)
Therefore, for two sides: \( 400 \text{ cm}^2 \times 2 = 800 \text{ cm}^2 \)
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Total surface area to decorate:
- Combine all the areas calculated: \[ \text{Total area} = \text{Front} + \text{Top} + 2 \times \text{Side} \] \[ \text{Total area} = 540 \text{ cm}^2 + 540 \text{ cm}^2 + 800 \text{ cm}^2 = 1880 \text{ cm}^2 \]
Therefore, the surface area of the box that needs to be decorated is 1,880 cm².