7 replies to this topic

[bonanova]

Inspector Craig of Scotland Yard was called to Transylvania to solve some cases of vampirism. Arriving there, he found the country inhabited both by vampires and humans. Vampires always lie and humans always tell the truth.

However, half the inhabitants, both human and vampire, are insane and totally deluded in their beliefs: all true propositions they believe false, and all false propositions they believe true. The other half of the inhabitants are completely sane: all true statements they know to be true, and all false statements they know to be false.

Thus sane humans and insane vampires make only true statements; insane humans and sane vampires make only false statements.

Inspector Craig met two sisters, Lucy and Minna. He knew that one was a vampire and one was a human, but knew nothing about the sanity of either. Here is the investigation:

Craig (to Lucy): Tell me about yourselves.
Lucy: We are both insane.
Craig (to Minna): Is that true?
Minna: Of course not!

Did Craig learn the vampire's identity?

[badhri]

Spoiler for The below is the only possible combination

 
Lucy - Vampire Sane
Minna - Human Sane

[TimeSpaceLightForce]

Spoiler for need clue

+-  --  ++  -+

sv  iv  sh  ih

 

if M is -+     +? -!   (-++-)= +

L tells  +  

if M is +-     +? -!

L tells  +

if M is --     +? -!

L tells  -

if M is ++     +? -!

L tells  -

 

if L is -+

L tells -  

if L is +-

L tells -

if L is --

L tells +  

if L is ++

L tells +

[bonanova]

Spoiler for The below is the only possible combination

 Lucy - Vampire Sane
Minna - Human Sane

Lucy's statement could not be true?

[Rainman]

Spoiler for Answer

If one were sane and the other insane, they would have agreed on that statement. So they are either both sane or both insane. If they are both sane, Lucy would have to be a vampire since she made a false statement. If they are both insane, Lucy would have to be a vampire since she made a true statement. Either way, Lucy is a vampire. Unless Craig is insane, in which case he would be wrong in believing that one is a vampire and one is human But since Craig is probably not from Transylvania, that is unlikely.

[badhri]

Lucy's statement could not be true?

Lucy - Vampire Sane
Minna - Human Sane

 

Lucy's statement - We are both insane - this is false (since both are sane)

Minna's statement - Of course not - this is true

 

Hope i m clear.. Ans: Lucy - Vampire

 

This can also be lucy - Vampire insane ; Minna- Human insane.. anyhow Lucy- vampire

[bonanova]

Lucy - Vampire Sane
Minna - Human Sane
 
Lucy's statement - We are both insane - this is false (since both are sane)
Minna's statement - Of course not - this is true
 
Hope i m clear.. Ans: Lucy - Vampire
 
This can also be lucy - Vampire insane ; Minna- Human insane.. anyhow Lucy- vampire

Right. I meant to ask could not Lucy be insane.

[TimeSpaceLightForce]

Spoiler for

+-  --  ++  -+

sv  iv  sh  ih

 

if M is -+     +? -!   (-++-)= +

L tells  +  

if M is +-     +? -!

L tells  +

if M is --     +? -!

L tells  -

if M is ++     +? -!

L tells  -

--------------

if L is -+

L tells -  

if L is +-

L tells -

if L is --

L tells +  

if L is ++             

L tells +                       

 

Minna is insane human leads to Lucy is insane vampire

Lucy can not be sane human if she tell true

Lucy can not be insane vampire  if she tell true

If minna is insane vampire can be sane vampire but one is human

if Lucy is insane can not tell false because both are insane.

If minna is sane human Lucy can tell false but both not insane

 

..not sure just follow the signs