Answer:
[tex]216\ km^2[/tex]
Step-by-step explanation:
1. Approach
The surface area of a three-dimensional figure is the two-dimensional distance around the figure. The easiest way to find the surface area of a figure is to find the area of each of its facets, then add up the area to get the total surface area. The given pyramid is composed of four congruent triangles and a square. Find the area of one of the triangles, and then the area of the rectangle. Multiply the area of the triangle by four to account for the fact that there are four congruent triangles. Then add the area of the base to the result, the result attained is the surface area of the prism.
2. Find the area of the triangles
The formula to find the area of a triangle is the following:
[tex]A_t=\frac{b*h}{2}[/tex]
Where (b) represents the base and (h) represents the height of the triangle. Substitute the given values into the formula and solve for the answer.
[tex]A_t=\frac{b*h}{2}[/tex]
[tex]A_t=\frac{9*7.5}{2}[/tex]
[tex]A_t=\frac{67.5}{2}[/tex]
[tex]A_t=33.75[/tex]
3. Find the area of the rectangle
The formula to find the area of a rectangle is the following,
[tex]A_r=b*h[/tex]
Substitute the given values in and solve,
[tex]A_r=b*h[/tex]
[tex]A_r=9*9[/tex]
[tex]A_r=81[/tex]
4. Find the total surface area
Multiply the area of the triangle by four to account for the fact that there are four triangles. Then add its area to the area of the rectangle.
[tex]A_t+A_t+A_t+A_t+A_r=A[/tex]
[tex]4(A_t)+(A_r)=A[/tex]
[tex]4*33.75+81=A[/tex]
[tex]135+81=A[/tex]
[tex]216=A[/tex]
