wolfgang

How can you weigh a living fish( which is more than 500 gm),found in an Aquarium? You are not allowed to: 1- take the fish out of water or out of the aquarium. 2- move the aquarium or weigh it. 3- replace the water with new one.

Yes....thats right...We love brainden

No... thats far away from the answer I am seeking

Or you can call them as " points to start from "

They are like Y axis

If G,T are 0,0 Find: T+3G-2 G+5 T-5T+2G-2 G-5T-2G-6G+2T-6 G-3G-2T-6

Yes....thats right

You have two baskets,each one contains 15 small balls( 5 Yellow,5 Red,and 5 Blue),you should exchange each two balls from one basket with one ball from the other basket,according to these roles: 1- Yellow+Yellow....... should be exchanged with a red ball. 2- Red +Red..........should be exchanged with a Blue ball. 3- Blue +Blue..........should be exchanged with a Yellow ball. 4- Yellow +Red..........should be exchanged with a Blue ball. 5- Red + Blue........should be exchanged with a Yellow ball. 6- Blue + Yellow.....should be exchanged with a Red ball. 7- each of the above exchanges will be considered as one step. Your aim is to get only ONE Yellow ball in one of these two baskets in less than 14 steps. Have a nice trial

If only a binary signaling scheme is allowed, CaptainEd has shown that only prisoner 1 needs to change his mind. Even in the stricter NS view, there are some latitude to define a quadnary signaling scheme due to an implied necessary condition You're right. NS signaling is enough. Four easily distinguishable rotations: None, 180ocw, 180occw, and 360occw. And entering prisoners must be able to see the rotation. I think we spent most of the time on this puzzle with a poor understanding of the conditions. But it was fun to finally solve something possible. It's just that the problem became teasing out the constraints that admitted a solution! Bertrand was helpful in this case. Thanks, Wolfgang. I want to thank you all....I was thinking like this: After the first three prisoners took their right places,they all should be facing the door, the possible combinations would be: Yellow,Green,Red,........ Yellow,Green,........,Blue Yellow,.........,Red, Blue .........,Green, Red, Blue so when the 4th one enters, Let him to have X color..the X one standing in the raw will turn his face to the wall,and the new comer will stand in that raw facing the door....and when nobody turns to the wall so he should stand at the empty place facing the door. when the four raws are made, each new comer will know where he belongs when the man with the same color turns his face toward the wall.

your method is successful with the first two prisoners, but you should find a very simple,uncomplicated way for the 3rd one,if you find it, the rest will be very easy and straight forward job.

A breath

This is a real one....on the inner wall of a W.C. someone wrote this with red paint" long live the communist party of russia " and underneath,another one replays with this " YES....but only in W.C. " !!

Shouldn't the OP be F=1, H=2,... etc.? In the alphabet of (f, h, n, y) k=1! Why should F=1?? Please see my above explanation How is "f=3" in that counting system? The letter "f" has no straight lines. Perhaps, you meant "F=3". Yes...I numbered them according to capital letters,but I asked the question using small letters to make it hard

Continuing with the community solve approach, can we clarify: Must all the persons in a particular row face the same direction? If prisoners in say the Yellow row can face in differing directions does that constitute [illegal] communication? Can the first two prisoners choose the time that they [legally] alter their position, at any time up to the last prisoner takes his place? During making raws...some of them can be..back to back (in any raw)...but by reaching the last prisoner,they all shoud be at the same direction But only the first two prisoners can move. This means the seventh prisoner, say can come into a row back to back with someone else in that row, then at a later time switch his direction so that at the end all in that row have the same direction. So as long as a prisoner stays in the same position, he can flip his direction back and forth during the formation of rows. That sounds like communication. Another piece of jello fell off the nail... Yes....in my OP I said....each prisoner should choose his raw and once he did,he is not allowed to change his mind,but turning around himself was not mentioned

Shouldn't the OP be F=1, H=2,... etc.? In the alphabet of (f, h, n, y) k=1! Why should F=1?? Please see my above explanation

Yes...the raws should be as you mentioned in your diagram,but all should face one direction

Continuing with the community solve approach, can we clarify: Must all the persons in a particular row face the same direction? If prisoners in say the Yellow row can face in differing directions does that constitute [illegal] communication? Can the first two prisoners choose the time that they [legally] alter their position, at any time up to the last prisoner takes his place? During making raws...some of them can be..back to back (in any raw)...but by reaching the last prisoner,they all shoud be at the same direction

I can add something which may help you... The raws may face the door or the opposit direction!

Yes...thats right....he should wait until the previous prisoner is standing in his raw and took his position.

I am at loss about the purpose of "Entering singly". "Not changing one's position once taken" seems to be a reasonable, good, and severe limitation upon those criminals, indeed. Conversely, if OP requires each conman to take his place in the formation before the next inmate enters the hall, then I cannot imagine what method could possibly exist for the condemned men? After all, the rows would start forming without any knowledge of the color on the forehead of the next culprit to enter... Yes, each one should choose his place where to belong,once he did, he is not allowed to change his mind.(Except the first two ...see OP)

hey WG this is a nice puzzle for my friends According to your method(NEWS),seems as if the first prisoner is giving a hint to the others,which is actually not allowed...see the roles in OP

I said in the OP",each one should himslf choose where to stay, once he did,he can not change his place".and with this method each one stays infront of 1 making a raw,so can not change his place.

The colors are not equal

I think the problem's set up in such a way that you can't use that strategy. The people are blindfolded until they enter the room. So the first person won't see anyone's color, the second person will only see the first person's color, etc. Just for clarification, are there set positions where each row should form? In other words, should we treat this as if there are four rows of seats and all of the yellows must sit in the first row and all the greens in the second row etc.? Or instead can they form rows wherever they want, so if the first person to enter is yellow he can he stand anywhere in the room as long as all the other colors stand somewhere behind him? They can form raws whenever they want