(True)man and (Liar)ry Riddle
Our weekly poker game has a pair of identical twins, Truman and Larry, whom no one can tell apart by looking at them. They both have a very unusual tell that easily would allow anyone to tell them apart. During and only during the game, Larry would lie every time he spoke while Truman would tell the truth every time he spoke. The eventual consequences of these compulsions were that neither would say anything during the game.
One week one of the brothers arrived late and took a seat at the table without saying anything. The other brother did not show up at all. No one knew which brother was playing and which one was absent.
A big pot, with over a $1000 in it, developed between Joe and the twin. On the end Joe was afraid he had a loser. Before he called a final $500 bet, Joe offered the twin $100 if he would look at Joe’s hand and answer one question with a yes or no. The twin accepted and answered the question collecting the $100. However, Joe called the final bet knowing he had won the pot. What was the question? How did he know which brother was playing?
(True)man and (Liar)ry Riddle Solution
Joe shows the twin his hand while asking, “If your brother were here and assessed my hand, would he say your hand beats my hand?” The twin said “Yes” and Joe confidently called.
If the twin playing were Larry, then he would lie about what his brother would truthfully say. Thus you should do the opposite of what he says. A “yes” meant he should call.
If the twin playing were Truman, then he would truthfully tell you what his lying brother would say. Thus you should do the opposite of what he says. A “yes” meant he should call.
He did not know which brother was playing. It did not matter.
