What flies around all day but never goes anywhere?
Riddle AnswerHard Riddles
Tractor on an Island
You are on an island in the middle of a lake. The lake is in a remote part of the country and there has never been a bridge connecting the island to the mainland.
Every day a tractor and wagon gives hay rides around the island. Puzzled as to how the tractor had gotten onto the island, you ask around and find out that the tractor was not transported to the island by boat or by air. Nor was it built on the island. Can you explain how the tractor got there?
Riddle AnswerI Am Always There, Some Distance Away
I am always there, some distance away, somewhere between land or sea and sky I lay, you may move toward me, yet distant I’ll stay. What am I?
Riddle AnswerBlind Bartender’s Problem
Four glasses are placed on the corners of a square Lazy Susan (turntable). Some of the glasses are upright (up) and some upside-down (down).
A blindfolded person is seated next to the Lazy Susan and is required to re-arrange the glasses so that they are all up or all down, either arrangement being acceptable.
The glasses may be re-arranged in turns subject to the following rules.
- Any two glasses may be inspected in one turn and after feeling their orientation the person may reverse the orientation of either, neither or both glasses.
- After each turn the Lazy Susan is rotated through a random angle.
- At any point of time if all four glasses are of the same orientation, a bell will ring.
Can you devise an algorithm which allows the blindfolded person to ensure that all glasses have the same orientation (either up or down) in a finite number of turns? The algorithm must not depend on luck.
Riddle Answer