A puzzle related to @The_Letter_Wriggler post #91790 in the Maths forum. It is taken from ‘Puzzles and Curious Problems’ by Henry Dudeney.
221. – THE FLY’S JOURNEY
A fly, starting from point A, can crawl round the four sides of the base of a cubical block in four minutes. Can you say how long it will take it to crawl from A to the opposite upper corner B?
The question is accompanied by a diagram where A and B are diametrically opposite points on the cube.