Henry Ernest Dudeney/Puzzles and Curious Problems/221 - The Fly's Journey

by : $221$

 * The Fly's Journey
 * A fly, starting from point $A$, can crawl around the four sides of the base of this cubical block in $4$ minutes.


 * Dudeney-Puzzles-and-Curious-Problems-221.png


 * Can you say how long it will take to crawl from $A$ to the opposite corner $B$?