a trianglular pyramid / what is the surface area

Question

a trianglular pyramid has a base with an area of 7 square centimeters and layeral faces with bases of 4 centimeters and height of 12 centimeters. what is the surface area of the pyramid

Answer 1

You need to add up the areas of the base and the lateral faces.  Since it is a triangular pyramid there are 3 lateral faces.  

 

The area of the base is given as 7 square cm

 

Each face is a triangle with base = 4 cm and height = 12 cm so each face has an area of 

 

A = (1/2)*base*height = (1/2)*4*12 = 24 square cm  

 

There are 3 lateral faces so the total surface area is 

 

3*A + 7 = 3*24 + 7 = 79 square centimeters