What is the surface area of the triangular pyramid? use the net of the pyramid to find the surface area.

Each of the triangles making up the sides and base have a base of 8 cm and a height of 6.9 cm. Then the area of the pyramid is that of 4 such triangles.
  A = 4×(1/2)×b×h
  A = 2×(8 cm)×(6.9 cm)
  A = 110.4 cm²

The surface area of the triangular pyramid is 110.4 cm².

What we must do is observe that the triangles have the same measurements.
 We have then that the surface area is:
 A = (4) * (1/2) * (b) * (h)
 Where,
 b: base of the triangle
 h: height of the triangle
 Substituting values:
 A = (4) * (1/2) * (8) * (6.9)
 A = 110.4 cm ^ 2
 
 The surface area of the triangular pyramid is:
 A = 110.4 cm ^ 2