The surface area of the regular triangular pyramid is 108 square centimetres.
Step-by-step explanation:
What is a regular triangular pyramid?
A triangular pyramid is a three-dimensional shape that has a triangular base and three triangular faces.
The lateral surface area is the area of all the sides of a 3-dimensional object excluding its base and top.
The surface area of a triangular pyramid is the sum of the areas of the four faces of the pyramid.
What is the surface area?
The area of one face = lateral surface area / 3
81 / 3 = 27
The surface area = 27 x 4 = 108