[ image courtesy of Futility Closet ]
Inside a rectangular room, measuring 30 feet in length and 12 feet in width and height, a spider is at a point on the middle of one of the end walls, 1 foot from the ceiling, as at A, and a fly is on the opposite wall, 1 foot from the floor in the centre, as shown at B. What is the shortest distance that the spider must crawl in order to reach the fly, which remains stationary? Of course the spider never drops or uses its web, but crawls fairly.
This puzzle was posted yesterday by Greg Ross, and he promised that he would publish the solution today. I am looking forwards to that. Greg classified this puzzle as “tricky”. I would not classify it as “tricky”, but rather as “not-so-obvious”. After some reasoning, one should be able to come up with a solution (which may not be unique).
I will await for Greg’s solution and comment on it. I will then present my own solution to the general case problem, and attempt to show you that this problem is deeper and richer than it may appear at first sight.