Jump to content
British Coin Forum - Predecimal.com

50 Years of RotographicCoinpublications.com A Rotographic Imprint. Price guide reference book publishers since 1959. Lots of books on coins, banknotes and medals. Please visit and like Coin Publications on Facebook for offers and updates.

Coin Publications on Facebook

   Rotographic    

The current range of books. Click the image above to see them on Amazon (printed and Kindle format). More info on coinpublications.com

predecimal.comPredecimal.com. One of the most popular websites on British pre-decimal coins, with hundreds of coins for sale, advice for beginners and interesting information.

Recommended Posts

33 minutes ago, Paddy said:

This is a famous old one, but maybe some here haven't met it before:

You are locked in a room with just doors out. One leads to safety, the other certain death. Also in the room are two robots - one can only tell the truth, and the other always lies, but you don't know which is which. They know which door leads to safety and you don't.

You are allowed just one question to one of the robots. What do you ask to ensure you know which is the safe door to open?

 

Logically, nothing. You will never know which of them is the liar. 

Pure Russian roulette - you might as well choose yourself. 

Share this post


Link to post
Share on other sites

Here's one for you:-

 

cables.jpg

Share this post


Link to post
Share on other sites

A more tricky chess puzzle. White to move and wins material permanently by move 3. Material means the number of points. Queen = 9, Rook = 5, Bishop and Knight =3, Pawn =1.

202924404_1-Copy.jpg.7b6b00307b129e247328d7fabb0cef98.jpg

 

Share this post


Link to post
Share on other sites
1 hour ago, Paddy said:

This is a famous old one, but maybe some here haven't met it before:

You are locked in a room with just doors out. One leads to safety, the other certain death. Also in the room are two robots - one can only tell the truth, and the other always lies, but you don't know which is which. They know which door leads to safety and you don't.

You are allowed just one question to one of the robots. What do you ask to ensure you know which is the safe door to open?

 

Which door would the other robot say is the safe door? Then whatever reply you get, go through the other door.

  • Like 1

Share this post


Link to post
Share on other sites
41 minutes ago, 1949threepence said:

Here's one for you:-

 

cables.jpg

The poles need to be touching.

  • Like 2

Share this post


Link to post
Share on other sites
Posted (edited)

I had my fun now and will let others have a go.

Edited by Sword

Share this post


Link to post
Share on other sites
56 minutes ago, Sword said:

Which door would the other robot say is the safe door? Then whatever reply you get, go through the other door.

The "other robot"? According to the rules as posted, you can only ask one, ergo: you will never know. The riddle is not capable of being solved.

 

Share this post


Link to post
Share on other sites
20 minutes ago, Bronze & Copper Collector said:

Touching

Correct.  

Share this post


Link to post
Share on other sites
Posted (edited)

You meet three Gods on a mountain top. One always tells the truth, one always lies, and one tells the truth or lies randomly. They are called Truth, False and Random. They understand English but answer in their own language, with ja or da for yes and no - but you don’t know which is which. You can ask three questions to any of the gods (and you can ask the same god more than one question), and they will answer with ja or da. What three questions do you ask to determine who’s who?

Edited by 1949threepence

Share this post


Link to post
Share on other sites
18 minutes ago, 1949threepence said:

The "other robot"? According to the rules as posted, you can only ask one, ergo: you will never know. The riddle is not capable of being solved.

I am not certain I follow you. You pick a random robot and ask "Which door would the other robot say is the safe door?" If you have picked the truth telling robot, he will point to the death door (assuming he knows the other robot always lies). If you picked the lying robot, then he would also point to the death door (because he knows that the truth telling robot would point to the safe door and so he lies and point to the death door). Either way you go through the other door.

Share this post


Link to post
Share on other sites
29 minutes ago, Sword said:

I am not certain I follow you. You pick a random robot and ask "Which door would the other robot say is the safe door?" If you have picked the truth telling robot, he will point to the death door (assuming he knows the other robot always lies). If you picked the lying robot, then he would also point to the death door (because he knows that the truth telling robot would point to the safe door and so he lies and point to the death door). Either way you go through the other door.

Precisely - we don't know because that factor is not built into the equation.

If it is, then your answer is obviously 100% correct. 

Share this post


Link to post
Share on other sites
Posted (edited)
2 minutes ago, 1949threepence said:

Precisely - we don't know because that factor is not built into the equation.

If it is, then your answer is obviously 100% correct. 

Oh but it is - you can ask one question of either robot, which is what Sword's answer gives.

Edited by Peckris 2

Share this post


Link to post
Share on other sites

A man is captured by cannibals who decide to kill and eat him. But their chief decides to offer the man a merciful end - he says "You can make one statement. If it's true, we will kill you quickly before putting you in the pot. If it's a lie, you will die horribly, boiled alive".

The man makes his statement. It makes the chief hopping mad but in the end there is nothing he can do but to release his captive. What was the man's statement?

Share this post


Link to post
Share on other sites
1 hour ago, 1949threepence said:

The "other robot"? According to the rules as posted, you can only ask one, ergo: you will never know. The riddle is not capable of being solved.

 

Yes it is. You say to whichever robot you choose: "If I were to ask the other robot which door he would say was safe, what would he answer?" Which ever you have asked you get one half truth and one half lie - making a lie overall, and so you choose the other door.

Share this post


Link to post
Share on other sites
6 minutes ago, Peckris 2 said:

Oh but it is - you can ask one question of either robot, which is what Sword's answer gives.

One can only tell the truth and one can only lie. You don't know which one is which, and nor do you know from the information given, whether either robot knows whether the other one tells the truth or lies. In that scenario, if the one telling the truth is asked that question, then he will truthfully answer, I don't know, meaning you still have a 50 50 chance. If you ask the one who's lying how the other would answer it wouldn't matter what door he pointed to, you would still have a 50 50 chance.  

Share this post


Link to post
Share on other sites
3 minutes ago, 1949threepence said:

One can only tell the truth and one can only lie. You don't know which one is which, and nor do you know from the information given, whether either robot knows whether the other one tells the truth or lies. In that scenario, if the one telling the truth is asked that question, then he will truthfully answer, I don't know, meaning you still have a 50 50 chance. If you ask the one who's lying how the other would answer it wouldn't matter what door he pointed to, you would still have a 50 50 chance.  

Ah yes. Missing from the puzzle as stated is the fact that each robot knows the nature of the other robot, whether they lie or not.

  • Like 1

Share this post


Link to post
Share on other sites
Posted (edited)
4 hours ago, Peckris 2 said:

Ah yes. Missing from the puzzle as stated is the fact that each robot knows the nature of the other robot, whether they lie or not.

A very valid point.

Interestingly enough though, I have no recollection of any presentation, in any variation, of this conundrum that I have seen wherein that stipulation is made.

It appears that the assumption is that truth and lies are absolutes and any specific knowledge is irrelevant...

Edited by Bronze & Copper Collector
  • Like 1

Share this post


Link to post
Share on other sites
Posted (edited)
12 hours ago, Sword said:

I am not certain I follow you. You pick a random robot and ask "Which door would the other robot say is the safe door?" If you have picked the truth telling robot, he will point to the death door (assuming he knows the other robot always lies). If you picked the lying robot, then he would also point to the death door (because he knows that the truth telling robot would point to the safe door and so he lies and point to the death door). Either way you go through the other door.

You can ask a conditional question. By doing so you ensure that it doesn't matter whether the robot being asked is a liar or atruth teller. So you ask ' if I  ask you if this is the safe door, would you say yes.'

Edited by DaveG38

Share this post


Link to post
Share on other sites

Staying sober.

Pretending I haven't seen this Midsummer Murder before.

Not eating yet another packet of crisps.

 

These are real daily challenges.

  • Haha 2

Share this post


Link to post
Share on other sites
2 hours ago, DaveG38 said:

You can ask a conditional question. By doing so you ensure that it doesn't matter whether the robot being asked is a liar or atruth teller. So you ask ' if I  ask you if this is the safe door, would you say yes.'

That's no good. If it was the truthful robot, you'd get the answer 'yes', but you'd also get the answer 'yes' from the lying robot if it WASN'T the safe door, so you'd be no better off.

Share this post


Link to post
Share on other sites
14 hours ago, Peckris 2 said:

A man is captured by cannibals who decide to kill and eat him. But their chief decides to offer the man a merciful end - he says "You can make one statement. If it's true, we will kill you quickly before putting you in the pot. If it's a lie, you will die horribly, boiled alive".

The man makes his statement. It makes the chief hopping mad but in the end there is nothing he can do but to release his captive. What was the man's statement?

Anyone?

Share this post


Link to post
Share on other sites
2 minutes ago, Peckris 2 said:

Anyone?

He could say “you’re going to boil me alive” ; that would provide the chief with an unresolvable conundrum.

Jerry

  • Like 2

Share this post


Link to post
Share on other sites

Let's hope the chief can keep his word better than our politicians...

Share this post


Link to post
Share on other sites
2 hours ago, blakeyboy said:

Staying sober.

Pretending I haven't seen this Midsummer Murder before.

Not eating yet another packet of crisps.

 

These are real daily challenges.

Have you got "Talking Pictures TV"? - many many old British films, and TV series, including comedy's. 

 

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×