For all polyhedra the number of edges is two less than the sum of the number of vertices and faces. This is shown in the formula \(E\) = \(V\) + \(F\) – 2 The flat surface of a cube is a face.

486 ÷ 6 = 81. The area of one square face of the cube is 81 cm². Image caption, Find the length of an edge of the cube by finding the square root of the area of a square face. √81 = 9.