Fill in the grid so that every row, every column, and every 3x3 box contains the digits 1 through 9. That's all there is to it. It doesn't sound like much, but it's as addictive as hell. The Times
is one publication with a daily puzzle (may be unavailable to overseas readers.) There a tuturial and sample puzzle here
posted by salmacis
on Dec 10, 2004 -
What Color is My Hat?
I [heart] these mathematical conundrums -- simple, easy-to-state, seemingly obvious logic problems that have solutions that completely defy common sense. Here's another you can spring on a friend: "You want to fry up three pieces of french toast. You have a frying pan that is just large enough to accomodate two pieces of bread at a time. If it takes you 30 seconds to fry one side of bread, and each piece of must be fried on both sides, how long will it take you to cook up three pieces (assuming that the act of flipping a piece or adding/ removing it to or from the pan takes no time). Think about it. Answer inside.
posted by Shadowkeeper
on May 25, 2001 -