Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫  π  -¹ ² ³ °

You are not logged in.

## #1 2013-03-28 01:43:29

anna_gg
Member
Registered: 2012-01-10
Posts: 232

### Logicians and stamps (again)...

An unknown number n of logicians will play the following game:
A moderator will stick two stamps on each logicians' forehead. He tells everyone that he has n+1 red stamps and n+1 black stamps. They do not know, however, that the moderator has already stuck one red and one black stamp on the forehead of each logician, except for one to whom he has stuck two red stamps.
The logicians are sitting on a circle so that anyone can see everyone else's stamps. The moderator asks them in turn, starting from the logician who is sitting in the position Nr 1, "what color are your stamps?" The logician with the two red stamps on his forehead is sitting in the position Nr x (unknown to us).
For which values of n and x the logician with the two red stamps can guess the color of his own stamps?

Last edited by anna_gg (2013-03-30 07:37:10)

Offline

## #2 2013-03-28 06:57:42

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,039

### Re: Logicians and stamps (again)...

A few questions:
Do they know which stamps the others have on their foreheads and do they know what color of stamps were the ones the moderator still has?

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

Offline

## #3 2013-03-28 10:59:29

anna_gg
Member
Registered: 2012-01-10
Posts: 232

### Re: Logicians and stamps (again)...

Yes they do because they are sitting on a circle, thus they can see each other's forehead.
No they don't know what color are the stamps that the moderator still has.

Offline