If you tried the bike try this one!

4 men are (A B C & D) buried up to their necks in the ground.  They can not move so can only look forward.  Between A and B is a brick wall which can not be seen through.  They know that between them are 4 hats, 2 x black and 2 x white, but they do not know which colour they are wearing.  In order to avoid being shot one of them must call out to the executioner the colour of their hat. If they get it wrong, everyone will be shot.  They are not allowed to talk to each other and have 10 minutes to fathom it out.

After 1 minute:

Q Which one of them calls out ?

Q. Why is he 100% certain of the colour of his hat ?

This is not a trick question.  There are no outside influences nor other ways of communicating. They cannot move and are buried in a straight line. So A & B can only see their respective sides of the brick wall, C can see B and D can see B & C.

D is the only one who can call out and he will only call out if both b & c are wearing the same colour hats.

C will answer the opposite to what B is wearing because, if he was wearing the same as B, then D would have already called out.

a man walks into a bar .....ouch

No cigars yet!

After 1 minute C calls out.  If D could see 2 hats of the same colour he would call immediately, so B and C are wearing one white and one black between them.  He is wearing the other hat - if he can see a white one it's black etc.

That's been tried though...........

This originated at the RAF fast jet training school at RAF Valley.  A class of 10 trainee "Top Guns" from the Fleet Air Arm and Royal Airforce all got the correct answer in under a minute. Non of you have yet. But then compared with a Sea Harrier a  Merlin Rocket is deady easy to drive. Though paradoxically I can think of a lot of pilots who sail thpough none who've done really well at boat speed! No doubt someone will show me to be wrong.

Could we have the answer please - posted as a separate thread so those that want to carry on torturing themselves still can!

I think you will find there are already 2 correct answers above !!

Thats what I thought but Mr T says apparently not?

A calls out!!
As B,C & D are systematically executed after getting it wrong, their hats fly in the air as the bullets strike and are visible above the wall allowing A to work out his hats colour.

As it is not mathemetical, as otherwise D would be the only certainty if he saw two colours ahead he would have the oppersite and there is a possiblity that D could see both B & W thus only having 50% chance, and thus that has been deemded incorrect, then perhaps it is physical, assuming they are burried up to their necks in sand in a desert during the middle of the day, either one of the prisoners with a black hat would call out after 1 minute once they feel their head warming up.

they all wait till the harriers fly by, blow their hats off and - voila!

But there are no outside influences, which would include the weather, which is of course impossible, so therefore it must be a mathematical problems as it is theorectical, and it isn't a trick question!

Hmmm....

....could be on a slope? but no tricks we are told  - still think C is correct!

Agree with Friday that it is C.  D would make the call only if B and C are the same colour hats. C is therefore in prime position to know this.  Poor old A and B haven't got a clue as they can't see what anyone is wearing.  They might be manic depressives tired of life and waiting for the weekend to arrive and call out in the hope that they are wrong and in this way end it all (PS it might help if they hated C and D as well)

Yes, C would, as D didn't make the call, but would C only wait 1 minute?   If D was a bit dense and hadn't worked it out in time then C would get it wrong.

However if C waited 9 minutes, to make sure D had time to make a choice, he would run the risk that one of the others would panic and make a wild guess on the basis that 50% chance of living is better than 0%.

get back 2 work!

D does not call out, so B assumes that B and C must have different colour hats as B knows that D can see B and C.

B can see C, and in the knowledge (D has not shouted out) that he has a different colour hat to C, B shouts out the opposite colour to C.

D would have shouted immediately. so it must be B shouting after one minute.  B trusts that Mr D is not having a laugh on this one

oops

got my B and C mixed around there!  could have been deadly in the circumstances.....

D does not call out, so C assumes that B and C must have different colour hats as B knows that D can see B and C.

C can see B, and in the knowledge (D has not shouted out) that he has a different colour hat to B, C shouts out the opposite colour to B.

D would have shouted immediately. so it must be C shouting after one minute. C trusts that Mr D is not having a laugh on this one

you guys need to get out more