Author Topic: Anyone for Logic?  (Read 8268 times)

Offline Bilthehut

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Anyone for Logic?
« on: July 23, 2010, 10:31:13 AM »
Cannibals ambush a safari in the jungle and capture three men. The cannibals give the men a single chance to escape uneaten.

The captives are lined up in order of height, and are tied to stakes. The man in the rear can see the backs of his two friends, the man in the middle can see the back the man in front, and the man in front cannot see anyone. The cannibals show the men five hats. Three of the hats are black and two of the hats are white.

Blindfolds are then placed over each man's eyes and a hat is placed on each man's head. The two hats left over are hidden. The blindfolds are then removed and it is said to the men that if one of them can guess what color hat he is wearing they can all leave unharmed.

The man in the rear who can see both of his friends' hats but not his own says, "I don't know". The middle man who can see the hat of the man in front, but not his own says, "I don't know". The front man who cannot see ANYBODY'S hat says "I know!"

How did he know the color of his hat and what color was it?

Jack

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Re: Anyone for Logic?
« Reply #1 on: July 23, 2010, 04:30:35 PM »
The man at the back didn't know, therefore the two in front weren't BOTH white, otherwise he'd have known his own had to be black. Which means the two in front were either black/white or black/black.

The middle guy didn't know either, which means that the hat in front wasn't white, otherwise he'd have known his own was black. Therefore the front guy's hat must have been black, and this is how he worked it out.

Of course, he's relying on the folks behind him being smart enough to think about such things.

Offline Diane CBPFC

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Re: Anyone for Logic?
« Reply #2 on: July 23, 2010, 04:35:54 PM »
If the cannibals were rich enough to own five cowboy hats and had such good English language skills, you would think they would have just ordered out for pizza wouldn't you.
People will come from strange lands to hear me speak my words of wisdom. They will ask me the secret of life and I will tell them. Then maybe I'll finish off with a song. The Nomad

Jack

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Re: Anyone for Logic?
« Reply #3 on: July 23, 2010, 04:43:12 PM »
Are cowboy hats expensive?

Anyway, perhaps they just saved the hats that belonged to folk they had previously eaten.

Although if cowboy hats are expensive, perhaps they could have sold them on eBay and made enough money for a pizza.

Offline Bilthehut

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Re: Anyone for Logic?
« Reply #4 on: July 23, 2010, 05:20:04 PM »
They were just hats, not especially cowboy ones. Anyway they probably could not afford the broadband connection to surf the net for eBay.

Offline Bilthehut

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Re: Anyone for Logic?
« Reply #5 on: July 23, 2010, 05:21:37 PM »
p.s. Congrats Jack. Good logic and explanation.

Offline Tarquin Thunderthighs lll

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Re: Anyone for Logic?
« Reply #6 on: July 23, 2010, 06:19:34 PM »
I didn't see any mention in the original question of the hats being cowboy hats. I think this is one of those trick questions that try to trick you into thinking they were cowboy hats, and thereby be confused, especially if you didn't know whether they were stetsons or ten-gallons, the latter being wibble-dribble snickypuff poddly-moddly mangold. I'll be right there, Auntie Cyril.
I apologise, in advance.

Offline Roger Kettle

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Re: Anyone for Logic?
« Reply #7 on: July 23, 2010, 08:05:17 PM »
I agree with Tarks.

Offline Bilthehut

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Re: Anyone for Logic?
« Reply #8 on: July 23, 2010, 11:02:16 PM »
How about this one, then?

Two boys wish to cross a river.
The only way to get to the other side is by boat, but that boat can only take one boy at a time.
The boat cannot return on its own, there are no ropes or similar tricks, yet both boys manage to cross using the boat.

How do they cross the river?

Offline Tarquin Thunderthighs lll

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Re: Anyone for Logic?
« Reply #9 on: July 23, 2010, 11:10:10 PM »
Are they wearing hats?
I apologise, in advance.

Malc

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Re: Anyone for Logic?
« Reply #10 on: July 23, 2010, 11:15:22 PM »
I know Jack has already answered this, but I wanted to see if we worked it out the same way.

There are five hats, three black, two white. Only three are used.

The rear is first to answer. He see the two hats in front but does not know which colour hat he is wearing. Therefore the two in front cannot both be white.
They could both be black, but the rear guy cannot be sure that he's wearing the third black hat.
Middle guy hears the rear guy's answer and knows that his and Front guy's hat cannot both be white.
Middle can see Front guy's hat.
If it is white, then Middle's own hat must be black, and he can answer.
If Front guy's hat is black, then Middle's could also be black, so Middle cannot answer.
Realising this, Front guy knows Middle guy's hat is black and so, therefore, is his own.

It should be noted that the natives didn't forbid the three captives to speak.
Therefore Rear guy could have said to middle guy "what colour features in the phrase 'as the ace of spades'?".
The middle guy would have said 'black' and that would have allowed him to guess his hat colour. Then they would all have gone free.

Offline Roger Kettle

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Re: Anyone for Logic?
« Reply #11 on: July 23, 2010, 11:17:11 PM »
I hate myself for even thinking about this, but nothing says they have to STAY across the river. Therefore, one of them could cross the river and then return with the boat, allowing the other to do the same. If this is wrong, I don't care.

Offline Bilthehut

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Re: Anyone for Logic?
« Reply #12 on: July 23, 2010, 11:20:48 PM »
I hate myself for even thinking about this, but nothing says they have to STAY across the river. Therefore, one of them could cross the river and then return with the boat, allowing the other to do the same. If this is wrong, I don't care.

It's not the answer I am after, but I cannot fault your logic in thinking outside the box.  Well done, Roger.  Now, anyone with the real answer.  They do cross the river and end up on the opposite side they started from.  And no, they are not wearing hats.

Offline Bilthehut

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Re: Anyone for Logic?
« Reply #13 on: July 23, 2010, 11:24:38 PM »
I know Jack has already answered this, but I wanted to see if we worked it out the same way.

There are five hats, three black, two white. Only three are used.

The rear is first to answer. He see the two hats in front but does not know which colour hat he is wearing. Therefore the two in front cannot both be white.
They could both be black, but the rear guy cannot be sure that he's wearing the third black hat.
Middle guy hears the rear guy's answer and knows that his and Front guy's hat cannot both be white.
Middle can see Front guy's hat.
If it is white, then Middle's own hat must be black, and he can answer.
If Front guy's hat is black, then Middle's could also be black, so Middle cannot answer.
Realising this, Front guy knows Middle guy's hat is black and so, therefore, is his own.

Your logic is sound, Malc.

It should be noted that the natives didn't forbid the three captives to speak.
Therefore Rear guy could have said to middle guy "what colour features in the phrase 'as the ace of spades'?".
The middle guy would have said 'black' and that would have allowed him to guess his hat colour. Then they would all have gone free.
What has this to do with the hat colour.  In any case, the third one got it right and they all lived to tell the tale.  How do you think this puzzle came to be?

Offline Bilthehut

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Re: Anyone for Logic?
« Reply #14 on: July 23, 2010, 11:49:01 PM »
Mary's mum has four children.
The first child is called April.
The second May.
The third June.
What is the name of the fourth child?