“do they still teach the ‘new math’ in school?” I asked Unlucky Louie. Five of his kids are still there. “No more,” Louie said. “There was the old math, next the ‘new math’ and then came the aftermath.”
The mathematical concept known as “restricted choice” is taken for granted, but when it was introduced about 60 years ago, it was quite controversial: The play of a card that might have been a choice of equals increases the chance that the player in fact had no choice.
Against two hearts, West leads the 10 of diamonds. South wins and leads a trump: jack, king, five. On the next trump, East plays the eight.
South can reason that if West had Q-J doubleton, he might have played the queen; if he had the jack alone, he had to play it. So South should finesse with his 10. (The reasoning would be the same if West played the queen on the first trump. But if South somehow knew that West would always play the jack from Q-J doubleton, the odds would shift back.)
In this deal, South should finesse in trumps even if he has never heard of “restricted choice.” What actually happened was that South played the ace. When West discarded, South led a spade, but East won, cashed his queen of trumps and led two more spades, forcing out dummy’s last trump. South lost two clubs and another spade and went down one.
South is safe if he finesses on the second trump. When the finesse wins, he draws the last trump and takes five trumps, two diamonds and one spade ruff in dummy. If the finesse lost, South could get two spade ruffs.