Answer:
The first step is to find the area of the base triangle:
Area = (1/2) x base x height
Area = (1/2) x 20 yards x 17.3 yards
Area = 173 square yards
To find the surface area of the pyramid, we need to find the areas of the four triangular faces and add them to the base area.
Area of a triangular face = (1/2) x base x height
Area of each face = (1/2) x 20 yards x 12 yards
Area of each face = 120 square yards
Now we can add up all the areas:
Surface area = base area + area of four faces
Surface area = 173 square yards + 4 x 120 square yards
Surface area = 653 square yards
Therefore, the surface area of the pyramid is 653 square yards.