The Riddle Of The Guards

[Welshman]

A man had been held prisoner by the enemy who had tortured and interrogated him to try to extract information.

Eventually, they decided that they would get nothing from him and that to hold him any longer was a waste of time.

However, they decided on one more torment for him.

They led him into a room. At the bottom of the room were two doors and, beside each door, stood an armed guard.

'We have no more use for you and we will let you determine your own fate. Walk through one of those doors, and you will walk to freedom. Walk through the other, and you will walk to certain death.

'To help you, you may ask just one guard just one question. However, one guard has been sworn to tell you only the truth, the other sworn to tell you only lies'.

'Oh, and you have just 10 minutes to decide on your question and choice. After that, the guards are instructed to shoot you where you stand'.

The prisoner gained his freedom - but what was the question he asked, and which guard did he ask?

[Thomas_Merton]

A man had been held prisoner by the enemy who had tortured and interrogated him to try to extract information.

Eventually, they decided that they would get nothing from him and that to hold him any longer was a waste of time.

However, they decided on one more torment for him.

They led him into a room. At the bottom of the room were two doors and, beside each door, stood an armed guard.

'We have no more use for you and we will let you determine your own fate.  Walk through one of those doors, and you will walk to freedom.  Walk through the other, and you will walk to certain death.

'To help you, you may ask just one guard just one question. However, one guard has been sworn to tell you only the truth, the other sworn to tell you only lies'.

'Oh, and you have just 10 minutes to decide on your question and choice. After that, the guards are instructed to shoot you where you stand'.

The prisoner gained his freedom - but what was the question he asked, and which guard did he ask?

<{POST_SNAPBACK}>

This one is nearly as old as I am - but I won't spoil it for those who don't know the solution.

[alvino]

He asked either guard to ask the other guard which door was the door to freedom. After receiving the answer, he entered the opposite door.

Reason being, if the guard he asked was the truthfull one, he would repeat what the liar said. If he asked the liar, he would tell the opposite of the truthfull one.

[Welshman]

He asked either guard to ask the other guard which door was the door to freedom.  After receiving the answer, he entered the opposite door.

Reason being, if the guard he asked was the truthfull one, he would repeat what the liar said.  If he asked the liar, he would tell the opposite of the truthfull one.

<{POST_SNAPBACK}>

That was quick ! Though not quite the way I first heard it. He asked either guard 'If I were to ask your friend is this the door to freedom, what would he say'.

If the answer was 'No' then that was the correct door - conversely, if the answer was 'Yes' then the other door was the one to go through.

[Thomas_Merton]

He asked either guard to ask the other guard which door was the door to freedom.  After receiving the answer, he entered the opposite door.

Reason being, if the guard he asked was the truthfull one, he would repeat what the liar said.  If he asked the liar, he would tell the opposite of the truthfull one.

<{POST_SNAPBACK}>

That was quick ! Though not quite the way I first heard it. He asked either guard 'If I were to ask your friend is this the door to freedom, what would he say'.

If the answer was 'No' then that was the correct door - conversely, if the answer was 'Yes' then the other door was the one to go through.

<{POST_SNAPBACK}>

It's the double negative that gives the positive - that is the solution.

Therefore the correct answer is the one you give.

Perhaps to avoid any other interpretation you ought to have added in the OP: the guards can only speak to him.

[Crossy]

The oldies are the best

The secret is to ask a question that will illicit the same answer from either guard.

Along the lines of 'if i was to ask him (point at other guard) the way out, what would he say?? and then exit through the other door.

Like Tom said it's the double-negative.

I also heard it that the guards can only talk to you.

[TizMe]

Its not a double-negative...

Its a positive-negative or a negative-positive....