Unit Posttest Type the correct answer in the box. Use numerals instead of words. A new building is formed by a square prism with a square pyramid on top. The base has an edge length of 60 feet, and the height of the prism is 150 feet. The height of the pyramid is one-sixth the height of the prism. What is the surface area of the exterior of the building rounded to the nearest hundred square feet? The surface area of the exterior of the building is approximately square feet.
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The Deep Dive
To find the surface area of the building, we first calculate the surface area of both the square prism and the square pyramid. 1. **Surface Area of the Square Prism**: The prism has 4 rectangular sides, and the top is covered by the base of the pyramid. - Area of the base = side² = 60² = 3600 sq. ft. - Area of the 4 sides = Perimeter of base × height = (4 × 60) × 150 = 36000 sq. ft. - Total surface area of the prism (excluding the top since it's covered by the pyramid) = 36000 + 3600 = 39600 sq. ft. 2. **Height of the Pyramid**: Height of the pyramid = 1/6 height of the prism = 1/6 × 150 = 25 ft. 3. **Surface Area of the Square Pyramid**: The area of the base is also 3600 sq. ft. The lateral surface area of the pyramid is calculated using the formula: - Lateral surface area = (1/2 × perimeter of base × slant height). - Slant height can be found using the Pythagorean theorem. - Half the base edge = 30 ft. - Using slant height = √(25² + 30²) = √(625 + 900) = √1525 ≈ 39.05 ft. - Lateral surface area = (1/2 × 240 × 39.05) ≈ 4686 sq. ft. 4. **Total Surface Area**: Total Surface Area = Surface area of the prism + Surface area of the pyramid (lateral only). Total Surface Area = 39600 + 4686 = 44286 sq. ft. Finally, rounding to the nearest hundred square feet gives us approximately **44300** square feet.