Lets do this by parts:
We have 3 rectangles of sides 18ft and 7ft; and 2 triangles of base 7ft and height 6.1ft
The area of a rectangle is side times side. Then, for each rectangle:
[tex]7ft\cdot18ft=126ft^2[/tex]
Then, we have 3 rectangles of area 126ft^2, the total of the three rectangles:
[tex]3\cdot126ft=378ft^2[/tex]
Now for the triangles, we know that the area of a triangle is base times height divided 2. THen:
[tex]\frac{7ft\cdot6.1ft}{2}=21.35ft^2[/tex]
We have 2 triangles, thus:
[tex]2\cdot21.35ft^2=42.7ft^2[/tex]
The total area is the sum of the areas of the rectangels and the triangles:
[tex]378ft^2+42.7ft^2=420.7ft^2[/tex]
The total surface area of the prism is 420.7ft²
