There are four equilateral triangles in the pyramid.
Determine the area of one triangle.
[tex]\begin{gathered} A=\frac{1}{2}\cdot7.79\cdot9 \\ =35.055 \end{gathered}[/tex]
The total area of four equilateral triangle is equal to the surface area of pyramid.
Determine the surface area of pyramid.
[tex]\begin{gathered} A^{\prime}=4\cdot35.055 \\ =140.22 \end{gathered}[/tex]
Thus surface area of pyramid is 140.22 square feet.
