Question

Each edge of a cube is coloured either red or
black. If every face of the cube has at least one
red edge, then the smallest possible number of
red edges is​

Answer 1

The total faces is 6

Each faces had 4 edges but not unique edges.

since edges are shared with one other face 6*4= 24

therefore 24/2 = 12 unique edges.

so at least one of the four edges is black.