Riddles and Puzzles

[BoganGod]

Two

[jonesthecurl]

Actually, i'd just mug the nearest one for the money and let them sort it out themselves.

[YoursFalsey]

Two

I'm going to neither confirm or deny Bogan's answer at this point- I would like to see some reasoning and/or the how ever many questions you would ask. I proposed this riddle without knowing the answer because I was working off the cuff at a public access computer. I improved on my initial answer, and I believe I proved to my own satisfaction that I cannot improve my final answer- however because I altered my own answer, I definately want to see the logic behind the answer.

[BoganGod]

Elementary my dear watsun. Simply ask the one person the same question twice, then use deductive reasoning! Nothing simpler

[spiesr]

Elementary my dear watsun. Simply ask the one person the same question twice, then use deductive reasoning! Nothing simpler

What question? Because asking the same person the same question twice let's you know which one he is, but not necessarily which of the other two Bob is.

[BoganGod]

The logical question about one of his brothers. Jeez, deductive reasoning must be low on the ground on this site. I tells ya.

[YoursFalsey]

Elementary my dear watsun. Simply ask the one person the same question twice, then use deductive reasoning! Nothing simpler

What question? Because asking the same person the same question twice let's you know which one he is, but not necessarily which of the other two Bob is.

Speiser's right. Repeating a question will let you know if you have the alternator. Repeating a question you already know the answer to will let you know which truth pattern you are dealing with (and whether you are catching the alternator on truth first or lie first) but you're goal is to find Bob, regardless of which truth pattern Bob has.

Suppose you twice ask one of the brothers "Are you Bob?". If you get yes twice, you don't know you have Bob telling the truth or Andy or Chad lying. If you get no twice, you don't know if you have Andy or Chad telling the truth or Bob lying. If you get one yes and one no, you know you've found the alternating triplet, but you still don't know if the yes was true and you asked Bob, or the no was true.

So keep pondering. (BTW, there is a hint in here to one solution, but you can find a better solution then the one hinted at...)

[YoursFalsey]

OK, Three identical triplets, Andy, Bob, and Chad.
Due to childhood trauma- their father was a sadistic professor of logic- one of them always lies, one of them always tells the truth, and one of them alternates true statements and false statements. Unfortunately, at the moment you cannot remember which is which. Suppose you are looking for Bob, because he owes you money, and run into two of the triplets. What is the minimum number of yes/no questions you must ask to guarentee you can determine which triplet (either one of the two, or the one who's not there) is Bob?

OK, here is a method to find Bob that uses four questions, all to the same triplet.
First question: Does Bob owe me money?
Second question: Does Bob owe me money?

If the triplet answers yes twice, you know he is the truth teller. If he answers no twice, you know he is the liar. If he answers yes then no, you know he is the alternater, and he will answer question three truthfully and question four with a lie. If he answers no and then yes, he is the alternator and will answer question three falsely and question four truthfully.

Third question: Are you Bob?
Fourth question: Is this brother Bob? (indicating the other present triplet.)

You know from your first two questions whether the triplets answers are lies or truths. With that knowledge, the answers to the last two questions reveal who is Bob.

[YoursFalsey]

Initially I thought that was the answer. After all, there are four possibilities for a triplets truthfulness, so it will take two yes/no questions to determine which of the four possibilities holds true. Likewise, there are three possibilities for which triplet is Bob, so will take two questions to determine once you know the triplets truthfulness. (You may get lucky and do it in one question, as one answer will correspond to one triplet and the other will correspond to two triplets, requiring a second yes/no question to determine which is Bob.) That was a minimum of four questions, although different questions or different orders would be possible.

Then I realized that I didn't ask for information about the truthfulness of who I was speaking to, only which triplet is Bob. So I only had three cases to sort between, and four yes/no questions should be overkill, able to sort between upto sixteen cases (2 to the fourth power) Logically, I thought there should be a way to do it in two questions, if I could only figure it out. I did figure it out. (Another reason why I neither confirmed or denied Bogangod's answer- I was curious whether he was guessing, knew a set of two questions, or had reasoned that two yes/no questions would be necessary to sort between three possiblilities but didn't know what they were.) So now I confirm Bogangod's two, and challenge someone to provide a set of two questions to determine which triplet is Bob.

[anonymus]

Initially I thought that was the answer. After all, there are four possibilities for a triplets truthfulness, so it will take two yes/no questions to determine which of the four possibilities holds true. Likewise, there are three possibilities for which triplet is Bob, so will take two questions to determine once you know the triplets truthfulness. (You may get lucky and do it in one question, as one answer will correspond to one triplet and the other will correspond to two triplets, requiring a second yes/no question to determine which is Bob.) That was a minimum of four questions, although different questions or different orders would be possible.

Then I realized that I didn't ask for information about the truthfulness of who I was speaking to, only which triplet is Bob. So I only had three cases to sort between, and four yes/no questions should be overkill, able to sort between upto sixteen cases (2 to the fourth power) Logically, I thought there should be a way to do it in two questions, if I could only figure it out. I did figure it out. (Another reason why I neither confirmed or denied Bogangod's answer- I was curious whether he was guessing, knew a set of two questions, or had reasoned that two yes/no questions would be necessary to sort between three possiblilities but didn't know what they were.) So now I confirm Bogangod's two, and challenge someone to provide a set of two questions to determine which triplet is Bob.

ok first i thought you could get it down to 3 by changing the first question you asked two times to something like; did i just speak but realized i was beeing a moron.. (since the alternating guy) so..
a)
1; hey bob! do you owe me money? yes/no
2; really bob do you owe me money? yes/no

if you are lucky and its actually bob you are talking to this would settle it in two questions.. (writing off top of my head here), but i guess if its the alternating guy you dont know if he starts on a lie or by telling the truth so this method doesnt really work either..

b)
aw hell i thought i could get up with another method by the time i got here but no.. id love to hear the actual sulotion though and since its been 2 weeks and no right answer (except bogan) maybe its time to reveal it?

really good one though mate

this one was tricky..

[YoursFalsey]

this one was tricky..

And here's the trick. To determine the truth of any proposition X, use the question, "Right now, would you say X?"
Suppose you are talking to the truthful triplet, or the alternator when he will be truthful. If X is true, he would say that X is true, and so he will truthfully tell you that he would say X is true. If X is false, he would not say X, and will truthfully tell you that he would not say so. Suppose you are dealing with the liar, or the alternator about to lie. If X is true, he would not say X, so he will lie and tell you yes, he would. If X is false, he would tell you X is true, so he will lie and tell you no, he wouldn't. You learn nothing about the triplet's honesty, but yes means X is true and no means X is false.

So question 1, ask the first triplet, "Right now, would you say you are Bob?" Question 2, ask the second triplet, "Right now, would you say you are Bob?" If one of the triplets answers yes, that's Bob. If you get two no's, you know the third triplet who isn't present must be Bob.

(And while I crafted the puzzle myself off remembered logic puzzles, it was Raymond Smullyan who first showed me the "would you say" trick. The right now I added in to deal with the alternator, who otherwise would say anything sooner or later.)

I could come up with another riddle, but prefer to give the floor to someone else at the moment...

[anonymus]

first of all hats off to YoursFalsey for constructing the hardest one yet here, and since noone is answering his call to take the floor, ill give you this little gem to chew on for a while..

Swings by his thigh / a thing most magical!
Below the belt / beneath the folds
Of his clothes it hangs / a hole in its front end,
stiff-set and stout / it swivels about.

Levelling the head / of this hanging tool,
its wielder hoists his hem / above his knee;
it is his will to fill / a well-known hole
that it fits fully / when at full length

He's oft filled it before. / Now he fills it again.

[slowreactor]

Is this really appropriate?

[anonymus]

:shock:

Is this really appropriate?

its just your dirty dirty mind playing tricks on you.. a child with no such impurities would probably get it in the first guess..

[YoursFalsey]

:shock:

Is this really appropriate?

its just your dirty dirty mind playing tricks on you.. a child with no such impurities would probably get it in the first guess..

I apparently only have a dirty mind rather then a dirty, dirty mind- I jumped to the same conclusion as slowreactor, but at least realized that was an intended false trail. A thorough one, though- I still haven't cleared my mind enough to see past it...

[hecter]

Switch. The probability that your original door hides the car is still 1/3, but the probability that the car is behind the other two doors is 2/3. You are in essence getting to trade your door for both of the others, increasing your chances of winning to 2/3.

Another way to put it:

3 possibilities -
1. You pick the car. Monty shows you goat A. You switch to goat B and lose.
2. You pick goat A. Monty shows you goat B. You switch to the car and win.
3. You pick goat B. Monty shows you goat A. You switch to the car and win.

4 possibilities.

4. You pick the car. Monty shows you goat B. You switch to goat A and lose.

[hecter]

first of all hats off to YoursFalsey for constructing the hardest one yet here, and since noone is answering his call to take the floor, ill give you this little gem to chew on for a while..

Swings by his thigh / a thing most magical!
Below the belt / beneath the folds
Of his clothes it hangs / a hole in its front end,
stiff-set and stout / it swivels about.

Levelling the head / of this hanging tool,
its wielder hoists his hem / above his knee;
it is his will to fill / a well-known hole
that it fits fully / when at full length

He's oft filled it before. / Now he fills it again.

The only guess I've got is a hammer...

[ender516]

Switch. The probability that your original door hides the car is still 1/3, but the probability that the car is behind the other two doors is 2/3. You are in essence getting to trade your door for both of the others, increasing your chances of winning to 2/3.

Another way to put it:

3 possibilities -
1. You pick the car. Monty shows you goat A. You switch to goat B and lose.
2. You pick goat A. Monty shows you goat B. You switch to the car and win.
3. You pick goat B. Monty shows you goat A. You switch to the car and win.

4 possibilities.

4. You pick the car. Monty shows you goat B. You switch to goat A and lose.

Possibilities 1 and 4 are really just one: You pick the car. Monty shows you one of the goats. You switch to the other goat and lose. Monty's choice of goats has no effect on the outcome.

[jonesthecurl]

Switch. The probability that your original door hides the car is still 1/3, but the probability that the car is behind the other two doors is 2/3. You are in essence getting to trade your door for both of the others, increasing your chances of winning to 2/3.

Another way to put it:

3 possibilities -
1. You pick the car. Monty shows you goat A. You switch to goat B and lose.
2. You pick goat A. Monty shows you goat B. You switch to the car and win.
3. You pick goat B. Monty shows you goat A. You switch to the car and win.

4 possibilities.

4. You pick the car. Monty shows you goat B. You switch to goat A and lose.

Possibilities 1 and 4 are really just one: You pick the car. Monty shows you one of the goats. You switch to the other goat and lose. Monty's choice of goats has no effect on the outcome.

Please, please let us not do this again. It is ver traumatic for me. Only one other time in my life did I get it so wrong, and a divorce fixed that...

[anonymus]

The only guess I've got is a hammer...

we have one guess, it is in the right direction if you are the brutal type or dont have access, but in the book the answer was something else..

[jonesthecurl]

Is this another of the anglo-saxon riddles? Sounds like it should be "a sword".

[ender516]

Is the item in question a key?

[Army of GOD]

Pant pocket?

[YoursFalsey]

Is the item in question a key?

I think ender516 is right- does that mean the next puzzle is Ender's Game?

(And if any one out there hasn't read Ender's Game, then they should go out and do so right now. It's that good. I'll wait.)

[anonymus]

Is the item in question a key?

I think ender516 is right- does that mean the next puzzle is Ender's Game?

Just like you pointed out the item is a key.. so next riddle goes to ender516 knock yourself out.. (also yes it was one of those anglo-saxan riddle-poems like someone pointed out..)