Re:Cute riddle: Four kids holding one toy balloon
by paulgb on Monday October 29, 2012 @11:02AM
(#4712543)
The two-nails problem is my favourite nerd-snipe. It can be explained to anyone without a math background, it can be solved on paper, it isn't a "trick" problem, and it isn't immediately easy.
The problem: hang a painting with one unbroken piece of rope going from one corner of the painting to another around two nails such that if either nail is removed the painting will fall.
"We show how to hang a picture by wrapping rope around n nails, making a polynomial number of twists, such that the picture falls whenever any k out of the n nails get removed, and the picture remains hanging when fewer than k nails get removed"