## 67. Fourth Round

In this round, one of the brothers, coming out of the house, said:

- Either I am Tralala with a card of black suit in my pocket, or I am Trulala with a card of red suit in my pocket.

Who was it?
67. Fourth Round (Red and Black). This time it is impossible to determine the suit (red or black) of the card of the one who came out of the house, but in either case, it should be Tra-la-la. Suppose he has a card of the red suit. Then he is telling the truth. Therefore, in front of Alice is either Tra-la-la with a black suit card or Tru-la-la with a red suit card. The first option is ruled out (since our hero has a red suit card). The second option remains, so in front of Alice is none other than Tru-la-la.

On the other hand, suppose he has a card of the black suit. Then the statement he made is false. Therefore, he cannot be either Tra-la-la with a black suit card or Tru-la-la with a red suit card. Hence, he is either Tra-la-la with a red suit card or Tru-la-la with a black suit card. The first alternative is ruled out (since it has been proven that he has a black suit card in his pocket). The second alternative remains: in front of Alice is Tru-la-la, as in the case analyzed above.