# Riddles

It does read kind of like that.

This one is rather well known -

You are wandering through the wilderness in the middle of the night and come up to a fork in the path.
There you meet two old men sitting on a large wood stump.
Legends tell that one of these old men speaks only the truth and that the other one always lies.
One of these paths leads to certain death while the other grants safe passage home. Both of those old men know about those two paths and which leads to which destiny.
You get to ask one of these two men one question.
Try to figure out, with this one question, asking one of the two men, which path is safe.

[tab]If you not gonna try doing it on your own, at least google it…[/tab]

[tab]I ask one of the men which path the other one would show me as being the safe one. The liar would lie and tell me the wrong path, because this is not what the other man would say. The truth teller would tell the truth and also show me the wrong path, because this is the lie which the other one would tell me. So both would tell me the wrong path and I would take the other one.[/tab]
[tab]I didn’t google it! But I knew the riddle :-" .[/tab]

True.

I tried to reconstruct this riddle with a friend a few years ago and even knowing roughly the key idea behind the solution* it still took quite some time to do so.

• [tab]that the question has to involve the other man in some way or form[/tab]

Up to now nobody has solved my last riddle (“Perfect Logicians”).

Six people in two groups.

There are six people A, B, C, D, E, F which are in each case either in group 1 or group 2. The following statements are given:

1. Both A and B are in 1.
2. F is in 2, and if E is in 2, then C is also in 2.
3. D is in 1 and if F is in 2, then A is also in 2.
4. A and E are both in 2.
5. D is in 2 and E is in 1, and if C is in 2, then B is in 1.
6. D and B are both in 2.
7. The statements 1-6 are wrong.

Who is in which group?

As it is worded, I don’t see how that one can end: “No’s all the way down.”

You know I haven’t studied logic and I have no good way to annotate, but I will make a start…

Start Moment:
A knows that B has 12, that A has 12 or 15, that B sees either 12 or 15 and no other number.
A says No.
B knows that A has 12 and that A has seen either 12 or fifteen on B. He knows he must have 12 or fifteen. If A has seen 15, then he is thinking either I have 9 or 12. If A has seen 12, then A is thinking I have either 12 or 15. B knows this is what A is thinking.
B says no.
A knows now that if B has seen 12 he is thinking that he either has 12 or 15. While at the same

I can imagine where one takes into account the limited possibilities and what the other must be thinking that at some point an elimination happens. But I cannot hold it in my head.

You are on the right way. Go on, please!

Write it down, if you can not hold it in your head, as you said.

Though I suspected such to be the intent of the puzzle, I also suspect the proposed solution to be fallacious. I currently don’t think that it can be solved that way, although misleading into the illusion of a solution. We’ll see.

1. A and B cannot both be in 1. Either A is in 1, B is in 1, or Neither are in one
Either A or B, or both A and B is in group 2.
2. F is undefined. E is undefined. C is undefined.
3. D is undefined. F is undefined. A is undefined.
4. Either A or E, or both A and E are in group 1.
5. D is undefined. E is undefined. C is undefined. B is undefined.
6. Either D or B, or both D and B are in group 2.

No solution.

If a statement is wrong, only one component may be wrong. Therefore, F is undefined.
For instance, in 2. F may be in 2, because only the end of the statment may be wrong. Therefore F is undefined

Solution to (“Perfect Logicians”)
[tab]A: Since he has 12, that means I do not have 9.
Case 1. I have 15. This means he thinks he has 12 or 9.
Case 2. I have 12. This means he thinks he has 12 or 15.
If I say no, that will tell him that he does not have nine, and that I know he does not have nine. Because if he had nine, that would mean I have 15. But I am unsure if I have 15.
“No.”
B: Him saying no means I do not have 9. Because if I had nine, he would know that his is 15. So he knows i do not have nine.
Case 1. I have 15. This means he thinks he has 12 or 9.
Case 2. I have 12. This means he thinks he has 12 or 15.
If I say no, that will tell him that he does not have nine, and that I know he does not have have nine, and that I know he does not have nine. Because if he had nine that would mean I know I have 15. But I am unsure if I have 15.
“No.”
A: Case 1. I have 15. Since I already made him know he doesn’t have 9, this means he would think he has twelve. Since he doesn’t know if he has twelve, this means Case 2 is true, that I have twelve.
“I have twelve.”
Three turns[/tab]

Sorry, but there is a solution.

Sorry, but that is false.

You need to learn to write. This makes no sense.

Menorca.

Obviously you are the only one here who is not capable of reading.

This riddle was alraedy solved by James S. Saint (viewtopic.php?f=4&t=188593&start=150#p2567357).

Again: Obviously you are the only one here who is not capable of reading.

Q.E.D.

PERFECT LOGICIANS

[tab]A: HIS IS 12 SO MINE MUST BE EITHER 12 OR 15. IF HE THINKS I SEE A 12 HE WILL THINK HIS IS EITHER 12 OR 15. IF HE THINKS I SEE A 15, HE WILL THINK HIS IS EITHER 9 OR 12.

“NO”

B: HE SAID NO, SO THAT MEANS I DON’T HAVE A 9. IF I HAD A 9 HE WOULD KNOW FOR SURE THAT HIS WOULD BE 15.
HOWEVER I STILL DON’T KNOW IF MY NUMBER IS 12 OR 15.

“NO”

A: WE BOTH KNOW THAT WE’RE NOT 9 AND THEREFORE THE OTHER EITHER 12 OR 15, BUT DON’T KNOW WHICH. WE CAN’T BOTH BE 15, SO IF I HAD 15 HE WOULD KNOW FOR SURE HIS IS 12. SINCE HE ANSWERED NO, I MUST HAVE A 12.

“BOOYAH, BITCHES”[/tab]

Hello again, Phoneutria.

The question of that riddle again: "After how many “no"s does the game end, if at all?”

Two, robot.