Toph Tucker | Fun | Riddles & Mind Tricks

There are _________ prisoners in a jail. The prison warden gives them one chance to get out. There is an room in the jail with two light switches. Every day, one prisoner will be randomly selected to be brought into the room. While there, they must flip one switch. If the prisoners can tell the warden with absolute certainty that every one of them has been in the room, he will let them go free.

The prisoners do not know what position the switches start out in. There are given five minutes to strategize right after the warden tells them the rules, but after that have no means of communicating - no leaving notes in the room, etching things on the walls, or anything like that. The switches are their only hope.

Hint: First figure out how they could do it if both switches started out down. Then adjust your answer so that it would work without the prisoners knowing the switches' original position.

Hint 2: Obviously, you can't represent ________ people in binary on only two switches. There must be another way to keep the total tally.

Answer:

#2: The Scale and the Bowling Balls [from Vivek Pai]

You have six bowling balls, and one is heavier than the rest. Using a scale, what is the fewest number of times you need to weigh the balls is order to determine which is heavier?

Hint: Don't use conventional thinking. Think outside the box.

Answer - How many times: 2 times

Answer - How: _______________??? GET FROM VIVEK

#3: Hat People [from Mr. McKinney]. See illustration at right.

You've got four guys each buried up to their necks in sand, or dirt, or something akin to that. (Who cares if their heads are actually floating slightly in the picture.) They only know that there are four people, and that two have white hats and two have black hats. People 1, 2, and 3 are facing towards the right; Person 4, behind a solid wall, is facing to the left. They can't see their own hats, they can't turn their heads any significant amount, they can't dig their way out, they can't communicate. We know that they are arranged as seen in the picture - black hat, white hat, black, white. Their goal is just that one of them - any one of them - needs to figure out what color hat he or she is wearing. How do they do it?

Hint: who can you eliminate from the question altogether? Is there anyone who's utterly helpless? Process of elimination...

Hint 2: imagine other possible setups - for example: white hat, black hat, black hat, white hat. Could anyone figure it out then? Could anyone eliminate certain setups?

Hint 3: Could anyone eliminate certain setups, i.e. because someone else would have already solved it? How does that knowledge benefit the person who realized it?

Answer: Person 4 is not the key; he can't see anybody, no one can see him. Person 3 can't figure it out, because all she sees is a wall. Person 1 sees a white hat and a black hat, which doesn't prove anything, so he can't figure it out. After a while of waiting, Person 2 must realize that no one else can figure it out, or else they already would have. If Person 1 can't figure it out, that means that People 2 and 3 have different color hats. So Person 2 knows that his hat is the opposite color of Person 3; Person 2 knows that he has a white hat. Problem solved. :)

http://www.straightdope.com/classics/a3_189.html

http://www.straightdope.com/columns/060203.html

http://blogs.starwars.com/hangover_boy/17/comments

Mind Tricks

#1: A scientist in a white lab suit with the nametag "Jon" comes up to you and says "I am holding an acid that can burn through anything instantly. It was discovered just hours ago at MIT." Should you believe him?
Answer: No. If it could burn through anything, then how would he keep it in a jar or his hand? It would just burn right through whatever was containing it!

#2: There are two ships of equal size and strength. One is made of steel and one of wood. Which one weighs more?
Answer: The wooden one. Pound for pound, steel is much stronger than wood.

#3: There are five adults, eight kids, four dogs and one baby all trying to fit under one umbrella. Who got wet?
Answer: No one; it wasn't raining.

#4: Why was George Washington buried at Mount Vernon?
Answer: Because he was dead.

#5: How far into a forest can you walk, no matter what the circumstances are?
Answer: Only half way; after that, you're walking out!

#6: Should you believe me if I said that a coin dated 20 B.C. had been found?
Answer: Silly billy, in 20 B.C., the term "B.C." wasn't even invented yet!

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Have any puzzlers you'd like to share? Let me know!

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