Imagine, if you will, that you needed the bird flu vaccine and time is
running out.  Before you are 2 Medical Administrators and 2 doors. 
One MA is standing in front of each door.  But what's behind the door,
you ask.  Well, in the room behind one of the doors is the bird flu
vaccine and in the room behind the other door is nothing.  You do not
know which door leads to which room, and that's where the MAs come in.
 The 2 MAs know which room has the vaccine, but the only problem is
that one MA always tells the truth and the other MA always tells a
lie.  And added to that, you do not know which MA is which.  They look
the same.  Here's your task: You can only ask one MA one question and
your goal is to get into that room with the vaccine, because as it was
previously mentioned, time is running out.  What is the one question
you ask the one MA to guarantee that you access the right room and
save yourself?  Hurry, time is running out.

Hello Macdonald,
 
The question would be:

"What door would the OTHER Medical Administrators tell me to go through?" 

(Listen to his answer, and then walk through the opposite door!)

Explanation: 

The Medical Administrators that always lies would lie, by saying
something like.... "That other MA will tell you to go through this
door" (Which is a lie in itself, remember- He ALWAYS LIES & can NEVER
tell the truth) Therefore, your recourse should be the wise move by
going through the OTHER door.

And likewise, the Medical Administrators that always tells the truth
would tell the truth, looking toward his counterpart and saying.... "
Him? Why he would tell you to go through this door!"



Read more about this kind of logic problem here:
Ask Dr Math - Liars & Truthtellers
http://mathforum.org/dr.math/faq/faq.liar.html


Other similar riddles:

http://www.sciam.com/article.cfm?articleID=000CC9E5-AE4C-11FF-A87E83414B7F0000

http://www.cut-the-knot.org/impossible/brothers.shtml

http://www.math.sunysb.edu/posterproject/www/materials/ask-right-question/ask-right-question.html


Search terms:
?always tells the truth?


I hope the information provided is helpful!

Best regards,
Bobbie7

---

Clarification of Answer by bobbie7-ga on 10 Oct 2006 10:24 PDT

Please excuse my typo.  

It should be "Medical Administrator" and not "Medical AdministratorS"

Has anyone else noticed that this was a duplicate question and
therefore answered twice now???

Steph53

Hi Steph53,

When I first locked this question I did not see a duplicate question.

After I posted my answer to this question, I noticed it. 

Unfotunatley, it was already locked by another researcher so I was not
able to post a warning.

It should be "Unfortunately"

Luckily both answers were the same!

Same as Bobbie. I didn't notice it either til after I answered it.