Looking at the basic probabilities
With the continuing COVID-19 crisis, bridge players have had few opportunities to play cards in person in the past year. For fans of the card game, we are offering a test of skills that pose questions about the strategies of playing in our weekly quiz.
We continue this week with another in the series of quizzes on basic bridge probabilities.
Today’s quiz: In the following problem, you are given your own and the dummy’s holding in two different suits and are asked to determine the best percentage play under the specified circumstances. You Dummy
S AQ5 S 432
D AK76 D 432
You are playing in a notrump contract and are in dummy for the last time. You need an additional trick and cannot afford to lose the lead to the opponents more than once. Should you play to set up your fourth diamond by conceding a trick to the opponents, or should you take a finesse by leading a spade to the queen?
Answer: The chance of a 3-3 break of the missing diamonds, which is what you will need to set up an extra diamond trick, is slightly more than onethird of the time (36%), while the spade finesse offers a 50% chance of success. If you had an additional entry to dummy, you could afford the delay the finesse and test the diamonds first. But, since you are in dummy for the last time, you should opt for the play that offers the better chance of succeeding in the long run.
If you had a fourth diamond in dummy, leaving the opponents with only five of them, the chance of a 3-2 split (68%) would alter the odds significantly, and you would play to set up an extra diamond trick rather than take the 50% spade finesse.