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# Masters of Logic Puzzles III. (stamps)

32 replies to this topic

### #11 dsu

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Posted 28 July 2007 - 07:06 AM

...umm what? didnt quite understand that one

A...B...C
if two have RR...
RR RR GG == C instantly has answer (sees all 4 R)
RR GG RR == B instantly has answer (sees all 4 R)
GG RR RR == A instantly has answer (sees all 4 R)
similarly if two have GG...

if two have RG...
RG RG RG == nobody can have any answer
RG RG RR == nobody can have any answer
RG RG GG == nobody can have any answer

RR RG GG
1st turn, nobody has the answer.
2nd turn, the person who sees one RR and one GG thinks:
If I had RR, the person having GG instantly must have had the answer.
If I had GG, the person having RR instantly must have had the answer.
But they did not...
So I have neither RR nor GG.
Therefore I have RG!
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### #12 xlm

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Posted 14 August 2007 - 11:35 PM

This puzzle is one move longer. Person A would be able to tell the second time, if B and C were RR GG or GG RR.
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### #13 singinsly

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Posted 18 August 2007 - 05:23 AM

Well, I think you stated this question wrong. Tech, they could have any from the way it is said, they could have purple-pink for all we know. You said a "set of 8". Set means 2. meaning 16. so even if moderator had red-red there still a bunch more out there.
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### #14 Wordblind

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Posted 24 August 2007 - 03:30 PM

I don't completely agree with the solution. It is true that B has one of each color, and C has to have some sort of pair. We just have no idea what A has.

The first three noes establish no two logicians have pairs of the same color. The fourth no, A's second, proves that A wasn't seeing two opposite-colored pairs. (She wouldn't have been able to have either type of pair, making her stamps obvious.) If C had a pair, B had to have one of each color, and it no longer mattered what A had.

Possible solutions:
-A- -B- -C-
RR RG GG
GG RG RR
RG RG GG
RG RG RR

So, A's ability to solve some configurations on her second turn stripped away some of the ambiguity that B faced in other configurations, thereby making it ambiguous as to which configuration was actually solved.

I would suggest shortening the puzzle so that it goes:
A: "No."
B: "No."
C: "No."
A: "Yes."

Sorry if anything is unclear, but it was taking much longer to express my view than it took to form it in the first place.
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### #15 Garyjamesstanton414

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Posted 25 September 2007 - 11:47 AM

Some of you people on here are such idiots.

The whole point of the puzzle is you need to work out the situation where

A: "No."
B: "No."
C: "No."
A: "No."
B: "Yes."

and what B's stamps are.

Why do you get people like Wordblind who start saying "its ambiguous". It is not ambiguous. There is only one solution.

B has 2 different coloured stamps (red and green)
A has a pair of stamps which are the same colour. (red or green).
C has a pair of stamps which are the same colour, but not the same colour as A's pair. (red or green).

It does not matter what colour A or C's pair are, all that matters is the situation. The situation being that both A and C will have the same colour stamps in their pair, and B will have stamps of different colours in B's pair.

Several people have already explained why this is the case. There are no other possible answers if you are being sensible and not just being a fool.
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### #16 ezephyr

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Posted 11 November 2007 - 12:20 AM

Well, I think you stated this question wrong. Tech, they could have any from the way it is said, they could have purple-pink for all we know. You said a "set of 8". Set means 2. meaning 16. so even if moderator had red-red there still a bunch more out there.

FYE for everyone. The statement in bold is incorrect. Set, while a very versatile word ("Set has 464 separate definitions in the Oxford English Dictionary, the most of any English word; its full definition comprises 10,000 words making it the longest definition in the OED." -From the Wikipedia disambiguation page) does not in any way limit itself to refering to twos. The word that singinsly was thinking of, I believe, was 'pair'. The 'official' Oxford English dictionary definition that most closely relates is: "a number of things or people grouped together as similar or forming a unit."

The key words here being 'a number'. Not 'two', 'a number', meaning any number. Nuff said.
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### #17 bigcitybrom

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Posted 30 November 2007 - 07:20 PM

took me a few mins, but I did figure it out.

B has GR

it is important to look at the responses

A said NO meaning A must have seen a RG(B.) and a RR©
B said no-B see's a GG(A) and a RR©
C said no see can see the RG(B.) and GG(A)
A says no again
B says yes after ruling out the answers of the others and what they must see and can't figure it out. Each of them must have seen a RG on B otherwise they would have answered yes because B saw two greens and two reds.

I hope that explanation makes sense.
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### #18 The Smelly Irishman

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Posted 13 January 2008 - 09:27 PM

This one is sub-par compared to the other riddles.
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### #19 LordDrakka

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Posted 21 February 2008 - 08:01 PM

the one that said yes knew because they had no stamp there were not enough to go around if the grand master took two away.
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### #20 Sean-in-Oz

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Posted 05 March 2008 - 04:54 AM

"Some of you people on here are such idiots????"

Mate, many folks are just learning to think logically here, and if they are taking the time to ask questions and learn, I would hardly call them idiots. On the other hand, someone who makes such arrogant statements about others . . . he in my opinion, would certainly deserve the label!

But in fairness . . . I agree no ambiguity here. B knows she is an RG.

To explain more politely why some went wrong, the puzzle states B was the first to say that she knew the colour of stamps. If the puzzle had been NO, NO, NO, YES, it would have meant that A had an RG. Similarly, if the puzzle had stated NO, NO, NO, NO, NO, YES, then C would have known she had an RG combo. But the puzzle said B knew in the second round, so that is the way we know she knew that she had an RG pair.

So what happens next?

A and C simultaneously ask if they can get extra credit, because they know not only what they have on their own heads, but also what is hidden in the Grand Master's pocket! B replies, that's silly ladies, everyone knows what is in the Grand Master's pocket. This one should be pretty easy, but how do they all know now?

OK I have an extension, variation on this one:

(Hopefully I've thought this one out properly, but if I have not I'd be happy to hear -- politely James!!!! -- why I my solution is incorrect)

In the next round, the answers are:
A: No
B: No
C: No
A: No
B: No
C: No
A: YES
B: No
C: YES
B: Bad Luck, looks like I lose this time! Can we play again?

Grand Master: Sure, why not, let me mix these up and paste them on again . . . OK ladies, you know the drill, your shot A . . .

A: No
B: No
C: No
A: No
B: No
C: No
A: No
B: No
C: No
A: YES
B: YES
C: YES
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