Answer:
702 ft²
Explanation:
The total surface area of the prism is the sum of the areas of its 7 faces.
lateral area
The width of each rectangular face is 8 ft. The total length of all of the rectangular faces is equal to the perimeter of the base:
7 ft +5 ft +3 ft +5 ft + 2 ft = 22 ft
So, the rectangular area is ...
A = LW = (8 ft)(22 ft) = 176 ft²
__
base area
The area of each base is equivalent to the area of a 5 ft×7 ft rectangle with a 3 ft×4 ft right triangle cut off one corner. The base area will be ...
A = LW -1/2bh
A = (5 ft)(7 ft) - 1/2(3 ft)(4 ft) = 29 ft²
__
area of one
So the total surface area of one structure is ...
lateral area + 2×(area of one base)
= 176 ft² +2(29 ft²) = 234 ft²
__
If 3 pieces are needed, the total amount of sheet metal needed for their construction is ...
(234 ft²) × 3 = 702 ft² . . . . needed to build all 3 pieces