All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars    
perplexus dot info

Home > Logic > Liars and Knights
Nine Native Narrative (Posted on 2010-02-06) Difficulty: 3 of 5
A very special island is inhabited only by knights and liars. Knights always tell the truth, and liars always lie.

Nine inhabitants of the island: Mel, Bart, Sue, Betty, Rex, Zeke, Sally, Zoey and Homer are busy at a conversation. A visitor from a neighboring island stops by and asks each of the nine inhabitants their respective identities. They say:

  • Mel: "Only a liar would say that Sally is a liar."
  • Bart: "Rex is a liar."
  • Sue: "Mel and Homer are liars."
  • Betty: "I know that I am a knight and Sally is a liar."
  • Rex : "Betty and I are both knights."
  • Zeke: "At least one of the following is true: that Sally is a knight or that Sue is a knight."
  • Sally:"It's false that Betty is a liar."
  • Zoey: "It's not the case that Sue is a liar."
  • Homer: "Betty is a liar or Zeke is a liar."
Determine the type of each of the inhabitants from the abovementioned statements.

No Solution Yet Submitted by K Sengupta    
Rating: 2.0000 (1 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Solution Analytical solution (spoiler) | Comment 2 of 3 |
a) Assume Betty is a knight. then Sally is a liar (based on Betty's statement).  But then Sally's lying statement implies Betty is a liar, which is a contradiction.  Therefore, Betty is not a knight.  Everything else follows quickly from this.

b) Since Betty is a proven liar, Rex's and Sally's statements are false, and Homer's is true.

c) Since Sally is a proven liar, Mel's statement is false.

d) Since Rex is a proven liar, Bart's statement is true.

e) Since Homer is a proven knight, Sue's statement is false.

f) Since Rex is a proven liar, Zoey's statement is false.

g) Since Sally and Sue are both proven liars, Zeke's statement is false.

So the only knights are Bart and Homer, just as Charlie's computer deduced.

  Posted by Steve Herman on 2010-02-06 16:51:16
Please log in:
Remember me:
Sign up! | Forgot password

Search body:
Forums (1)
Newest Problems
Random Problem
FAQ | About This Site
Site Statistics
New Comments (5)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Copyright © 2002 - 2019 by Animus Pactum Consulting. All rights reserved. Privacy Information