Good Riddles

 
Two Us=? (medium)

Question: What do you call 2 Us?

Question: A prison has 23 prisoners in 23 different cells. The prisoners have no way to communicate with each other in any way from their cells. There is another room, the rec room, that has two switches on the wall (A and B). The switches have on and off positions but they start in an unknown position.

Prisoners are randomly taken to and from the rec room one at a time. They must change the position of only one of the two switches each time they go to the room. At any point a prisoner can yell out, "Every prisoner has been here!" If the prisoner is correct that all of the prisoners have visited the rec room, then they all go free. If they aren't correct then they are all executed.

Before they start they are given one planning session during which they can discuss a method to win the game. What method can they use to ensure they all go free?

Riddle #179 (medium)

Question: Joe deals himself and his friend John some cards from a deck of cards (not the same amount). If John gives Joe some cards Joe will have 4 times as many cards as John. If Joe gives John the same number of cards he will have 3 times as many cards as John.

How many cards does each man have and how many cards do they trade?

By Bist

Question: Imagine that you enter a room, but the door shuts behind you and you are locked inside. The room is 3 meters high, and 6 meters x 6 meters as a square form. It is dark, the floor is metal just like the walls and the ceiling. You cannot destroy the walls, ceiling, floor or door. How to you get out?

Riddle #2972 (medium)

Question: what type of alley can you play in?