Jump to content


Welcome to BrainDen.com - Brain Teasers Forum

Welcome to BrainDen.com - Brain Teasers Forum. Like most online communities you must register to post in our community, but don't worry this is a simple free process. To be a part of BrainDen Forums you may create a new account or sign in if you already have an account.
As a member you could start new topics, reply to others, subscribe to topics/forums to get automatic updates, get your own profile and make new friends.

Of course, you can also enjoy our collection of amazing optical illusions and cool math games.

If you like our site, you may support us by simply clicking Google "+1" or Facebook "Like" buttons at the top.
If you have a website, we would appreciate a little link to BrainDen.

Thanks and enjoy the Den :-)
Guest Message by DevFuse
 

Photo
- - - - -


  • Please log in to reply
17 replies to this topic

#1 roolstar

roolstar

    Advanced Member

  • Members
  • PipPipPip
  • 250 posts
  • Gender:Male

Posted 28 January 2008 - 05:27 PM

OK, I thought of this one myself, So I hope I will not find it somewhere on this Board!!


In the land of Knights, Commoners & Knaves:
The Knights can only say the truth
The Knaves can only lie
The Commoners can go either way

WHAT IS THE QUESTION THAT KNAVES CANNOT ANSWER?

& A follow-up question

WHAT IS THE QUESTION THAT KNIGHTS CANNOT ANSWER?

Have fun!
  • 0

#2 roolstar

roolstar

    Advanced Member

  • Members
  • PipPipPip
  • 250 posts
  • Gender:Male

Posted 28 January 2008 - 05:44 PM

Follow-up 3:
WHAT QUESTION CAN THE KNIGHT ANSWER IN 2 DIFFERENT WAYS?

Foolow-up 4:

WHAT QUESTION CAN THE KNAVE ANSWER IN 2 DIFFERENT WAYS?

WOW I'm on fire....
  • 0

#3 roolstar

roolstar

    Advanced Member

  • Members
  • PipPipPip
  • 250 posts
  • Gender:Male

Posted 28 January 2008 - 06:10 PM

Oh and YES OR NO answers only allowed!
  • 0

#4 roolstar

roolstar

    Advanced Member

  • Members
  • PipPipPip
  • 250 posts
  • Gender:Male

Posted 28 January 2008 - 06:19 PM

And if you want to be really smart, do not use paradoxes like:

Did the chiken come before the egg?
  • 0

#5 bonanova

bonanova

    bonanova

  • Moderator
  • PipPipPipPip
  • 5918 posts
  • Gender:Male
  • Location:New York

Posted 28 January 2008 - 11:11 PM

Spoiler for Knaves cannot answer ...
Spoiler for Knights cannot answer ...
Spoiler for Knaves can answer two ways...
Spoiler for Knights can answer two ways...

  • 0
The greatest challenge to any thinker is stating the problem in a way that will allow a solution.
- Bertrand Russell

#6 unreality

unreality

    Senior Member

  • Members
  • PipPipPipPip
  • 6370 posts

Posted 29 January 2008 - 03:13 AM

For bonanova's unsolved #3 the answer is obviously:

Spoiler for answer

  • 0

#7 roolstar

roolstar

    Advanced Member

  • Members
  • PipPipPip
  • 250 posts
  • Gender:Male

Posted 29 January 2008 - 01:43 PM

Spoiler for Knights can answer two ways...


Spoiler for The two permited answers are


Spoiler for Knaves cannot answer ...:


Spoiler for Not really sure about that...



Very small hint: The answer I was looking for in case [1] will help provide the answers for the rest of the cases!!! And has actually a definite answer!


My advice: Try to find a different answer for case [1]...
  • 0

#8 roolstar

roolstar

    Advanced Member

  • Members
  • PipPipPip
  • 250 posts
  • Gender:Male

Posted 29 January 2008 - 01:54 PM

For bonanova's unsolved #3 the answer is obviously:

Spoiler for answer



Nice try...

A bit violent though... :D

Spoiler for But still i did not fully understand it

  • 0

#9 bonanova

bonanova

    bonanova

  • Moderator
  • PipPipPipPip
  • 5918 posts
  • Gender:Male
  • Location:New York

Posted 30 January 2008 - 11:59 AM

So it seems you're posing this problem:

[1] There is a Yes/No question Q1 whose known answer does not depend on the reply given when it's asked.
[2] There is a Yes/No question Q2 whose known answer does not depend on the reply given when it's asked.
[3] If you ask a Knave Q1, he cannot answer it.
[4] If you ask a Knight Q2, he cannot answer it.
[5] What are Q1 and Q2?

What we know about Knaves and Knights tells us that

If a Knave knows Q1's answer is Yes [No], he will say No [Yes].
If a Knight knows Q2's answer is Yes [No], he will say Yes [No].

I confess I don't see any room for a riddle here, and wait with interest to hear the answer.
  • 0
The greatest challenge to any thinker is stating the problem in a way that will allow a solution.
- Bertrand Russell

#10 roolstar

roolstar

    Advanced Member

  • Members
  • PipPipPip
  • 250 posts
  • Gender:Male

Posted 30 January 2008 - 01:56 PM

So it seems you're posing this problem:

[1] There is a Yes/No question Q1 whose known answer does not depend on the reply given when it's asked.
[2] There is a Yes/No question Q2 whose known answer does not depend on the reply given when it's asked.
[3] If you ask a Knave Q1, he cannot answer it.
[4] If you ask a Knight Q2, he cannot answer it.
[5] What are Q1 and Q2?

What we know about Knaves and Knights tells us that

If a Knave knows Q1's answer is Yes [No], he will say No [Yes].
If a Knight knows Q2's answer is Yes [No], he will say Yes [No].

I confess I don't see any room for a riddle here, and wait with interest to hear the answer.


You are right about all of the above.

remember that I started this thread during my thinking process in your puzzle "Four Knight and Knave problems". So if you want to give this another shot before spoiling the answer, try to trace back my thoughts there...

Spoiler for And here's my answer:


Remember that this is a puzzle I made up, just because I found it very interesting that there are some questions that cannot be answered and not because they will make people fall into a paradoxical situation...

I await your critique on the answer or your take at the rest of the cases anxiously...

Edited by roolstar, 30 January 2008 - 02:03 PM.

  • 0




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users