Friday Puzzle 2 -- Another truthteller/liar puzzle

4/17/09, 12:56 PM #1

Alex Yeilding
Guest

Friday Puzzle 2 -- Another truthteller/liar puzzle

We're on an island similar to the one Dan mentioned a couple of weeks ago, but on this island there are:

Knights, who always tell the truth, and are said to be of highest rank;

Knaves, who always lie, and are of lowest rank; and

Normals, who sometimes lie and sometimes tell the truth, of middle rank.

We meet three people, A, B, and C, and know that there is one of each type. A and B make the following statements:

A: "B is of higher rank than C"

B: "C is of higher rank than A"

Then C is asked: "Who has higher rank, A or B?" What does C answer?

Re: Friday Puzzle 2 -- Another truthteller/liar puzzle

4/17/09, 1:33 PM #2

Lee Schierer - McKean, PA
Guest

Re: Friday Puzzle 2 -- Another truthteller/liar pu

They're both liars! :)

Lee

Re: Friday Puzzle 2 -- Another truthteller/liar puzzle

4/17/09, 2:46 PM #3

Alex Yeilding
Guest

No :-(

Re: Friday Puzzle 2 -- Another truthteller/liar puzzle

4/17/09, 3:30 PM #4

Bill Earl
Member
Offline
948 posts

Registered: 6/17/05

Re: Friday Puzzle 2 -- Another truthteller/liar pu

B>A

Re: Friday Puzzle 2 -- Another truthteller/liar puzzle

4/17/09, 3:57 PM #5

Alex Yeilding
Guest

;-)

Re: Friday Puzzle 2 -- Another truthteller/liar puzzle

4/17/09, 4:00 PM #6

Dan Donaldson
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Offline
5,264 posts

Registered: 9/17/01

Re: Friday Puzzle 2 -- Another truthteller/liar pu

I am going to guess before I read Bill's so if I get it right, then hooray, but if I miss it, all will know also ;-)

C is the knight, B is the Normal, and A is the knave.

C will say that B>A

- - -

I have been woodworking for about 25 years now, and would consider myself an enthusiastic amateur. My claim to fame (or infamy) has always been fixing stuff. I spent time in the Air Force in the 60's then went to work as an electronic technician for civil service. I finally got my EE, and being fed up with the civil service nonsense, took a job with Ford Motor Company until I went with the split to Visteon last year. I got interested in music and started playing in a bluegrass band. I wanted a new guitar, and that kind of led me into woodworking. I bought some books, a few tools, and built a guitar. Luckily, I didn't know any better than to try that as a first ever project. I still play it when I get a chance, so it must not be too bad if it can live for over 20 years. After a stint in Mexico for my job, I moved into a new house and built a small shop. Since then I have been collecting tools and skills, probably more of the former than the latter ;-). Finding this site has done more for my skills and enjoyment than anything else. I have learned a lot and really enjoy the friendships that I have made here. I have been married to LOML (Lori) for 32 years now and have 6 kids. When they are all gone, I want to get a 1 bedroom house (so there is not room for them to move back in) and at least a 6 car heated/air conditioned garage for a shop. (Dream on...)

Re: Friday Puzzle 2 -- Another truthteller/liar puzzle

4/17/09, 4:52 PM #7

Alex Yeilding
Guest

Right answer but wrong reasoning

Your answer is right, but the case you mention is only one possibility.

A might be a

(1)Knight

(2)Normal

(3)Knave

Your solution is case 3. But consider case 1:

A says B>C, which we know is true, so A>B>C. B, being a normal can answer however he wants; his answer won't invalidate the case. C, being a knave, will lie about the relationship between A and B, so will say that B>A. Same answer as yours, but a different case.

Now consider whether B can say what he said if A is a normal. That lets you rule out case 2.

Re: Friday Puzzle 2 -- Another truthteller/liar puzzle

4/17/09, 10:23 PM #8

Dan Donaldson
Member
Offline
5,264 posts

Registered: 9/17/01

Re: Right answer but wrong reasoning

OOPs ;-) You know the funny thing is that I actually should have seen that from the analysis that I did. The case was there and identified, but I didn't see it after I saw the first one. ;-(

- - -

I have been woodworking for about 25 years now, and would consider myself an enthusiastic amateur. My claim to fame (or infamy) has always been fixing stuff. I spent time in the Air Force in the 60's then went to work as an electronic technician for civil service. I finally got my EE, and being fed up with the civil service nonsense, took a job with Ford Motor Company until I went with the split to Visteon last year. I got interested in music and started playing in a bluegrass band. I wanted a new guitar, and that kind of led me into woodworking. I bought some books, a few tools, and built a guitar. Luckily, I didn't know any better than to try that as a first ever project. I still play it when I get a chance, so it must not be too bad if it can live for over 20 years. After a stint in Mexico for my job, I moved into a new house and built a small shop. Since then I have been collecting tools and skills, probably more of the former than the latter ;-). Finding this site has done more for my skills and enjoyment than anything else. I have learned a lot and really enjoy the friendships that I have made here. I have been married to LOML (Lori) for 32 years now and have 6 kids. When they are all gone, I want to get a 1 bedroom house (so there is not room for them to move back in) and at least a 6 car heated/air conditioned garage for a shop. (Dream on...)

Re: Friday Puzzle 2 -- Another truthteller/liar puzzle

4/18/09, 1:55 AM #9

Alex Yeilding
Guest

And it took more than 4 minutes, to boot! ;-)

Re: Friday Puzzle 2 -- Another truthteller/liar puzzle

4/18/09, 2:00 AM #10

Dan Donaldson
Member
Offline
5,264 posts

Registered: 9/17/01

;-)

- - -

I have been woodworking for about 25 years now, and would consider myself an enthusiastic amateur. My claim to fame (or infamy) has always been fixing stuff. I spent time in the Air Force in the 60's then went to work as an electronic technician for civil service. I finally got my EE, and being fed up with the civil service nonsense, took a job with Ford Motor Company until I went with the split to Visteon last year. I got interested in music and started playing in a bluegrass band. I wanted a new guitar, and that kind of led me into woodworking. I bought some books, a few tools, and built a guitar. Luckily, I didn't know any better than to try that as a first ever project. I still play it when I get a chance, so it must not be too bad if it can live for over 20 years. After a stint in Mexico for my job, I moved into a new house and built a small shop. Since then I have been collecting tools and skills, probably more of the former than the latter ;-). Finding this site has done more for my skills and enjoyment than anything else. I have learned a lot and really enjoy the friendships that I have made here. I have been married to LOML (Lori) for 32 years now and have 6 kids. When they are all gone, I want to get a 1 bedroom house (so there is not room for them to move back in) and at least a 6 car heated/air conditioned garage for a shop. (Dream on...)

Friday Puzzle 2 -- Another truthteller/liar puzzle

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