The surface area of the triangular pyramid is 832.75 in².
What is the surface area?
Surface area = 5/2 × side base (apothem + slant height)
Where,
side base = 12 in
Apothem = 247.75/30 in²
Slant height = 19.5 in
So,
Surface area = 5/2 × side base (apothem + slant height)
= 5/2 × 12 × (247.75/30 + 19.5)
= 60/2 × (247.75+585) / 30
= 30 × 832.75/30
= 832.75 in²
Therefore, 832.75 in² is the surface area of the pyramid.