To find the total surface area of the triangular pyramid, we need to calculate the area of the base quadrilateral triangle and the area of the three triangular faces.
The area of the base quadrilateral triangle can be calculated using the formula for the area of a triangle: (1/2) * base * height = (1/2) * 15 inches * 13 inches = 97.5 square inches.
Next, we need to find the area of a single triangular face. The formula for the area of a triangle can be used: (1/2) * base * height = (1/2) * 15 inches * 18 inches = 135 square inches. Since there are three identical triangular faces, the total area of all three faces is 3 * 135 square inches = 405 square inches.
Adding the area of the base and the total area of the three faces gives us the total surface area of the triangular pyramid, as there are no other faces to consider. So, the total surface area is 97.5 square inches (base) + 405 square inches (faces) = 502.5 square inches.
To calculate the amount of fabric needed, we simply need to consider the total surface area. The area of fabric needed will be 502.5 square inches.