A set of 12 rods, each 1 metre long, is arranged so that the rods form the edges of a cube. Two corners, A and B, are picked with AB the diagonal of a face of the cube.

An ant starts at A and walks along the rods from one corner to the next, never changing direction while on any rod. The ant's goal is to reach corner B. A path is any route taken

by the ant in travelling from A to B.

(a) What is the length of the shortest path, and how many such shortest paths are there?

(b) What are the possible lengths of paths, starting at A and finishing at B, for which the ant does not visit any vertex more than once (including A and B)?

(c) How many dierent possible paths of greatest length are there in (b)?

(d) Can the ant travel from A to B by passing through every other vertex exactly twice before arriving at B without revisting A? Give brief reasons for your answer.

I have a solution for a) and b), which I did by just experimenting and counting the ways. Not sure about them though, and wasnt able to work out the next 2.

a) 2 metres, and 2 ways

b) I got 2, 4 or 6 metres