Backgammon

WHEN SHOULD you play on for a gammon rather than taking the sure point by doubling your opponent out? The arithmetic is quite simple. You must be twice as likely to win a gammon as you are to lose the game. This is because, with the cube on 1, if you win a gammon you will win one extra point, whereas if you lose you will lose one point and also the point you would have won by doubling your opponent out. Thus the 2:1 ratio.

In money play this situation only arises with redoubles, as the Jacoby rule eliminates the chance of winning a gammon with the cube on 1. In tournaments, however, this arises quite often. Look at the position above. Should black take a sure point by doubling or should he play on?

It is hard to see how black can lose this game unless white rolls exactly 33 in the next couple of rolls. With any 5 or 10, black will hit the white blot on his three-point and the most likely result is that white will end up with three men on the bar and black will win an easy gammon. Note also that if white does get an anchor on black's three-point, black can probably double him out later.

Black can play on for the gammon with very little risk of losing the game and should do so. Were the position more volatile - black's advantage could quickly disappear - then he should be more circumspect about playing on.