To find the total surface area of Monica's room that will be painted, we will calculate the areas of the four walls, the ceiling, and the floor.
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Walls:
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There are two pairs of opposite walls.
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The area of the two longer walls (20 ft. long and 9 ft. high): \( 2 \times (20 , \text{ft} \times 9 , \text{ft}) = 2 \times 180 , \text{sq ft} = 360 , \text{sq ft} \)
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The area of the two shorter walls (15 ft. wide and 9 ft. high): \( 2 \times (15 , \text{ft} \times 9 , \text{ft}) = 2 \times 135 , \text{sq ft} = 270 , \text{sq ft} \)
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Total wall area: \( 360 , \text{sq ft} + 270 , \text{sq ft} = 630 , \text{sq ft} \)
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Ceiling:
- The area of the ceiling (20 ft. long and 15 ft. wide): \( 20 , \text{ft} \times 15 , \text{ft} = 300 , \text{sq ft} \)
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Floor:
- The area of the floor (20 ft. long and 15 ft. wide): \( 20 , \text{ft} \times 15 , \text{ft} = 300 , \text{sq ft} \)
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Total Surface Area:
- Total area = Area of walls + Area of ceiling + Area of floor
- Total area = \( 630 , \text{sq ft} + 300 , \text{sq ft} + 300 , \text{sq ft} \)
- Total area = \( 630 , \text{sq ft} + 600 , \text{sq ft} = 1230 , \text{sq ft} \)
Therefore, the total surface area of the room that Monica is going to paint is 1230 square feet.