# A Riddle Using Deductive Reasoning

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### #41 Fjuri

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Posted 30 January 2016 - 01:32 AM

The prince new his father very, very well.

Next time I'll use my own wording instead of copying it from a website.

### #42 mike the wiz

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Posted 30 January 2016 - 04:19 AM

Yeahhh......that's semi-plausible I suppose. Perhaps you could say that he had pulled the same trick in the past, but I still think it's a bit of a hole in the riddle. (but there were no holes in my bicycle riddle)

Now how about my Two-Guards riddle? CLUE: it just requires you INVENT a solution. (don't worry if you can't get it, every person fails to solve a lot of riddles, even very clever people. But it is the FUN of trying to solve it that should be enjoyed, IMHO.)

You come up to two passageways with a door in front of each, and a guard on each door, you have to go down one of the passages. One leads to freedom the other leads to death. One guard always lies, one guard always tells the truth. The first guard says, "my way leads to freedom". The other guard says, "my way leads to freedom".

You can ask one guard one question in order to determine which path to take. What question will you ask?

(this riddle is just to test our ability to think with ingenuity, there is no correct answer, just as long as you come up with an answer that works.

### #43 piasan

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Posted 30 January 2016 - 11:54 PM

Yeahhh......that's semi-plausible I suppose. Perhaps you could say that he had pulled the same trick in the past, but I still think it's a bit of a hole in the riddle. (but there were no holes in my bicycle riddle)

Now how about my Two-Guards riddle? CLUE: it just requires you INVENT a solution. (don't worry if you can't get it, every person fails to solve a lot of riddles, even very clever people. But it is the FUN of trying to solve it that should be enjoyed, IMHO.)

You come up to two passageways with a door in front of each, and a guard on each door, you have to go down one of the passages. One leads to freedom the other leads to death. One guard always lies, one guard always tells the truth. The first guard says, "my way leads to freedom". The other guard says, "my way leads to freedom".

You can ask one guard one question in order to determine which path to take. What question will you ask?

(this riddle is just to test our ability to think with ingenuity, there is no correct answer, just as long as you come up with an answer that works.

I would ask some question that has only one true answer such as: "What is two plus two?"  That would tell you if the guard you asked is truthful.

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### #44 Fjuri

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Posted 31 January 2016 - 10:48 AM

You come up to two passageways with a door in front of each, and a guard on each door, you have to go down one of the passages. One leads to freedom the other leads to death. One guard always lies, one guard always tells the truth. The first guard says, "my way leads to freedom". The other guard says, "my way leads to freedom".

You can ask one guard one question in order to determine which path to take. What question will you ask?

(this riddle is just to test our ability to think with ingenuity, there is no correct answer, just as long as you come up with an answer that works.

Here's my reply from previous time:

I know the answer to that famous riddle so I won't post it.

I would ask some question that has only one true answer such as: "What is two plus two?"  That would tell you if the guard you asked is truthful.

"One. We can only count modulus 3."

### #45 piasan

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Posted 31 January 2016 - 01:23 PM

I would ask some question that has only one true answer such as: "What is two plus two?"  That would tell you if the guard you asked is truthful.

"One. We can only count modulus 3."

I just knew some smart-ash was going to come up with an answer in a different number system.

Notice, I didn't say what the correct answer to 2+2 would be.  I also said it would be a question that has only one true answer.

If you don't like 2+2, we can always ask what color is a green grape?  Which reminds me of a bonus question my geometry students were given:  "What subject is this class."  Only 2 out of more than 100 even answered it.

BTW, in a modulus 3 number system, 2+2=11.

### #46 Fjuri

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Posted 01 February 2016 - 01:05 AM

I just knew some smart-ash was going to come up with an answer in a different number system.

Notice, I didn't say what the correct answer to 2+2 would be.  I also said it would be a question that has only one true answer.

If you don't like 2+2, we can always ask what color is a green grape?  Which reminds me of a bonus question my geometry students were given:  "What subject is this class."  Only 2 out of more than 100 even answered it.

BTW, in a modulus 3 number system, 2+2=11.

So you gave an example that wasn't valid.

Modulus systems are different in the US? If we follow these definitions. There is no second number part.

Lets take the riddle back to its original form.

"You come up to two passageways with a door in front of each, and a guard on each door, you have to go down one of the passages. One leads to freedom the other leads to death. One guard always lies, one guard always tells the truth. The first guard says, "my way leads to freedom". The other guard says, "my way leads to freedom".
You can ask one guard one question in order to determine which path to take. What question will you ask?"

Now your question has to involve the passage to take because knowledge of which guard lies is no longer sufficient.

### #47 mike the wiz

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Posted 01 February 2016 - 04:12 AM

Piasan is basically right.

All you have to do is ask one of the guards a question you know the answer to and he knows the answer to forcing him to lie.

"Are you human?" The one that always lies will have to say, "no". The one that always tells the truth will have to say, "yes".

Or, if he is wearing a red top. "Are you wearing a red top?" Basically you FORCE the lie or force the truth, either giving you knowledge of the liar.

### #48 Fjuri

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Posted 01 February 2016 - 04:16 AM

Of course he is basically right. Now solve the variant I provided:

"You come up to two passageways with a door in front of each, and a guard on each door, you have to go down one of the passages. One leads to freedom the other leads to death. One guard always lies, one guard always tells the truth. The first guard says, "my way leads to freedom". The other guard says, "my way leads to freedom".
You can ask one guard one question in order to determine which path to take. What question will you ask?"

### #49 mike the wiz

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Posted 01 February 2016 - 04:31 AM

I shall try and overcome my learning difficulties and attempt to solve it but they sure slow me down because I have to fight the fog every time I think about things my mind can swap and conflate easily. I can never solve liar/truth riddles because I can't "hold" it in my head, as to who is the liar. Poor short term memory. Drives me bonkers so I may well leave it to Piasan this one.

### #50 mike the wiz

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Posted 01 February 2016 - 05:17 AM

You would ask one of them this one question; "if I were to ask you two questions and I asked you both the question of which path led to freedom would you both give the same answer, and then if you were to tell me which path was yours would you say it was the path to freedom? si in this scenario if it were really happening, what would your answers be to those two questions"

The liar would say, "My answers would be no, we would not both give the same answer and my answer as to which path is yes/no" (lies, as he always lies)

The truth teller would say, "yes, we would both give the same answer to the first question and I would tell you as to which path either, yes/no" (true, as they both would either both say yes or both say no if asked that first question, hypothetically speaking)

### #51 Fjuri

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Posted 01 February 2016 - 05:34 AM

You can't ask 2 questions... Hint: Try and squeeze those into one question.

I suggest you write it down if short term memory is an issue.

### #52 mike the wiz

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Posted 01 February 2016 - 06:20 AM

Yeah I think I have it now though "holding it" in my head is a bit like trying to give birth to an elephant from my back passage.

If it was the liar he would say, "he would say that I would say "yes" we would give the same answer and then he would say his passage was X/not X"

If it was the truth teller he would say, "he would say I would say no to the first question then say his passage was X/not X"

and now I think I shall have a headache for three hours from trying to keep it all in my head. Lol

### #53 Fjuri

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Posted 01 February 2016 - 07:52 AM

I think you got my hint wrong. "So what would be the other guard's answers if he was asked which answers you would give?" requires 2 answers to be given. I don't think you can count that as correct.. (ie you can't wish for more wishes and the like)

But! You got part of it right though:

The liar would lie about true answer the truther would give. The truther would truth about the answer the liar would give. Resulting in always a lie.

### #54 mike the wiz

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Posted 01 February 2016 - 11:16 AM

I think I get it, yes. I hate this type of riddle. Lol

### #55 Bonedigger

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Posted 01 February 2016 - 07:13 PM

Of course he is basically right. Now solve the variant I provided:

"You come up to two passageways with a door in front of each, and a guard on each door, you have to go down one of the passages. One leads to freedom the other leads to death. One guard always lies, one guard always tells the truth. The first guard says, "my way leads to freedom". The other guard says, "my way leads to freedom".
You can ask one guard one question in order to determine which path to take. What question will you ask?"

This is a classic riddle that it's been so long since the first time I came across it, I forget where (probably in a Piers Anthony book). Fjuri's "variant" is actually the standard riddle.

The solution is you ask one of the guards which door the other guard would say is the correct door. If you have asked the guard that always lies, then the other guard would truthfully report the correct door, and the guard you have asked will lie about the other guard's answer and give you the false door. If you have asked the guard that always tells the truth, then he will truthfully report the false door the other guard would give as an answer. In either case, the correct door is the door other than the one given by the guard you asked.

### #56 mike the wiz

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Posted 02 February 2016 - 04:36 AM

Well done BD. Yeah I get the logic pretty quick with these riddles but my bad short memory won't allow me to "hold" anything in my mind for long without it going *puff* and it's all gone.

One game I kind of like is countdown, which I sometimes watch on TV. 30 seconds to find a word in a set of letters, you have to get the biggest word you can. Here is a link to it, though I must say I was dazzled at first as all the rules had changes so I only scored 30 points.

http://www.pacdudega...games/countdown

### #57 mike the wiz

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Posted 16 May 2016 - 07:40 AM

Wine Bottles Riddle.

You have ten bottles full of wine on a shelf. You also have one empty bottle. You have to empty each and every one of the ten full bottles of wine. You cannot drink the wine or pour it away.

### #58 piasan

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Posted 16 May 2016 - 10:53 AM

Wine Bottles Riddle.

You have ten bottles full of wine on a shelf. You also have one empty bottle. You have to empty each and every one of the ten full bottles of wine. You cannot drink the wine or pour it away.

This is probably too simple.....

Pour the first bottle into the empty.  Then pour the second into the first, the third into  the second, the fourth into the third .... and so on.  You will end up with bottle #10 being the empty bottle.

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### #59 mike the wiz

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Posted 16 May 2016 - 11:06 AM

You get someone else to drink them.

### #60 mike the wiz

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Posted 16 May 2016 - 02:05 PM

"You had it your way once Piasan Khan...are you game for a re-match?" - Captain Kirk. - The Wrath Of Khan.

Two caged animals riddle.

You have two cages. One is glass which is sealed with an animal in it. There is no door, it just has little holes so it can breathe, and tiny crumbs and water to survive. You also have a wooden hut/cage which again, is sealed and only has holes in it.

You are starving and must eat something from one of the cages, but you cannot touch the animals in the cages. You also can NOT touch the wooden cage/box with a tool.

In the wooden box there is any animal of your choice.

You have your cooking tools ready and MUST eat soon. The animals are well fed and have been there for weeks. Nobody is around, you are close to starving to death now.

You can have ONE tool of your choice.

How do you get to eat? And what is the animal in the wooden box?

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