The surface area of a pyramid consist of the lateral surface which is the area of the number of triangles which form the sides (or faces) of the figure along with area of the base, which may be any polygon.
The lateral area of a right pyramid is the sum of the areas of the triangles forming the faces of the pyramid. In a right pyramid, by definition, these are congruent triangle. Also by definition, the base of a right pyramid is a regular polygon. Therefore, the base of the triangular faces is equal and their altitudes are also equal and are equal to the slant height of the pyramid.
Rules:

The lateral area of a right pyramid equals to the perimeter of the base times onehalf the slant height.

Total surface area = lateral surface area + area of the base

Slant height,
Example:
A pyramid on a square base has four equilateral triangles. For its other faces each edge being cm; find the whole surface.
Solution:
Let be the pyramid on the square base . As the side face are equilateral triangles of each side cm, therefore, the side of the square base is cm.
Area of the base square cm
Area of one side face
Area of all the four sides faces square cm
Area of the whole surface square cm.