Declarer is not expected to play every hand as though all 52 cards are exposed, but, despite this, he should only rarely fail to get the most out of a hand.

The nature of the game is such that sound reasoning is usually well-rewarded. If declarer realizes after a hand is over that he went down in a contract he could have made, he should review his plays objectively to see whether he could reasonably have found the winning line of play.

Take this case where South failed in a slam after winning the spade lead with the ace, drawing trump and finessing the jack of clubs. East took the king and returned a spade to put a quick end to the proceedings.

It might seem unfair to condemn declarer for having lost a trick to East’s singleton king, but, just the same, South should have made all the tricks!

As soon as dummy comes down, declarer can see that a successful finesse in either diamonds or clubs would allow him to discard his spade loser and make the slam.

Choosing one finesse over the other is not a matter of luck, even though theoretically there’s a 50-50 chance that West has either king.

The deciding factor is that opting to take the diamond finesse is better because it can be preceded by the play of the ace of clubs, which has a chance of catching the singleton king in either opponent’s hand.

This possibility should not be ignored because, mathematically, when four to the king of suit are missing, the king will be singleton about one time in eight.

Of course, if the king does not fall on the ace, declarer has the diamond finesse in reserve, and in that way, he gets two chances to make the slam instead of just one.

Tomorrow: You too can be a genius.