Ponder This

Every night, my 70-something mother does the crossword puzzle in the newspaper. She started doing it because someone told her puzzles help keep the mind sharp. The funny thing is, she calls me for the answers. I mostly help her out with the pop-culture references she wouldn’t have a clue about (like a couch-jumping scientologist=Cruise).

If you’re the type who likes puzzles or just the bragging rights that come with solving a problem, you might want to try matching wits with some IBM researchers. Every month, IBM Research—and puzzlemaster Oded Margalit—offers a new challenge on the IBM Web site. The “Ponder this” challenge tests your math and logic skills, and solvers are in good company with some of the best brains.

This month’s challenge is:

What is the probability that the last move in a backgammon game will be a double? To make things easier, we assume that all the 15 checkers of each player are at their 1-point (just ready to bear-off); so each player, in its turn, removes (bear-off) two checkers for every non-double throw and four checkers for every double.

The “Ponder this” site lists the people who solve it correctly and eventually—after about a month or so—posts the answers.

So if, like my mother, want to keep your mind sharp, give the IBM Research challenge a try and let me know if you get a prestigious solver listing. Just a warning: I’ll be of no help whatsoever with these puzzles. Better call your own kid.