Logic Puzzle #4

[Mean Dean]

OK, this is a very difficult one. Don’t stress out if you don’t solve it!



You’re in a room with 2 computers. 1 always tells the truth. 1 always lies.

The room has 2 doors. 1 leads to safety, and 1 leads to death.

2 computers, 2 doors, OK?

Your task is to formulate 1 question that you can ask of either computer, that will lead you to safety.

You get 1 question to ask, of either computer, that will lead you to safety.

What’s the question?

Dean

[katlady]

Why am I still up? It's 2 in the morning I really should go to bed. I would ask the computers which one computer is lying about number 2 being the safe door?

[Mean Dean]

Close, but no cigar.....

Dean

[Manuel]

I would say ( if I would ask you which is the safe door what would you tell me?)

TM

[Mean Dean]

Manuel,

No cigar, again........

This is a logic question, a question you guys may never have been faced with before.

You need to ask a universal question, one that, posed to either computer, will give you the door to safety.

You can't formulate a question to ask of just one computer. It must work with either computer. It must account for every variable, and be able to achieve a correct response from whichever computer you ask.

Continuing on,

Dean

[Manuel]

if you ask that question to each computer the one that lies would tell you the same answer as the one that tells the truth.

TM

[Phil&Liz]

Originally Posted by Manuel

if you ask that question to each computer the one that lies would tell you the same answer as the one that tells the truth.

TM

If I understand the question, you may only ask one computer one question, not each computer one question.

I sent this to my dad who is a Mensa member....lets see just how smart they really are !!!

Phil & Liz

[Rev22:17]

Dean,

Originally Posted by You

OK, this is a very difficult one. Don’t stress out if you don’t solve it!



You’re in a room with 2 computers. 1 always tells the truth. 1 always lies.

The room has 2 doors. 1 leads to safety, and 1 leads to death.

2 computers, 2 doors, OK?

Your task is to formulate 1 question that you can ask of either computer, that will lead you to safety.

You get 1 question to ask, of either computer, that will lead you to safety.

What’s the question?

Dean

This problem involves the classic solution of double negation to neutralize the liar.

My question: If I were to ask which door leads to safety, which door would you choose?

>> If asked which door leads to safety, the computer that answers correctly would in fact pick the door that leads to safety. When asked which door it would pick in response to that question, it again answers correctly and thus responds with the door that leads to safety.

>> Conversely, if asked which door leads to safety, the computer that answers wrongly would pick the door that leads to death. When asked which door it would pick in response to that question, however, it must answer incorrectly and thus responds with the door that leads to safety.

Thus, both computers pick the door that leads to safety in response to the question as posed.

Norm.

[katlady]

Very clever Norm.

[Mean Dean]

Ok, it's been long enough, so that we can give the correct answer.

Norm came the closest to the correct answer, but just missed it.

The correct answer (or question, if you will!) is:

"What would the other computer say if I asked it which is the door to safety?" And then you use the opposite door.

Let me explain:

Let's assume Door A leads to safety, and Door B leads to death.

If you ask the the truthful computer the question, it will respond truthfully and say that the lying computer will lie and say Door B.

If you ask the lying computer the question, it will lie, and say the truthful computer will say Door B leads to safety.

In either case, you use the opposite door of what the computer tells you.

Dean