that contains three blue and two red caps. The men are positioned in indian file in front and facing a wall. The man closest to the wall we shall call A. The second man standing behind A and also facing the wall we will call B, The third man standing behind B and also facing the wall we will call C. Caps are taken out of the box at random and placed on the heads of the three men. Of course, C can not see the color of his cap but can see the caps on A and B. B cannot see his cap nor C's cap but can see A's cap. Finally, A cannot see neither his nor A's and B's cap. C is asked if he knows the color of his hat and, after thinking for a few moments, answers that he doesn't know. Then the same question is asked of B who, after thinking for a few moments also answers that he doesn't know. Finally, A is asked the same question and, after thinking for a few moments, answers correctly. Now, the question is: What is A's cap color and how did he know?
2006-07-07
13:02:47
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10 answers
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asked by
Pavi
2
in
Science & Mathematics
➔ Mathematics
Ignore the question sign after the word "box" in the second sentence. For whatever reason this site does not allow me to edit the questions!
2006-07-07
13:05:53 ·
update #1
To Nelson de Blue: You don't have a clue of what is going on, do you?
2006-07-07
13:46:56 ·
update #2
To Nelson De Bon: You don't have a clue about what this is all about, do you?
2006-07-07
14:24:06 ·
update #3
To Jinx: You make abxolutely no sense! Read the question again!
2006-07-07
14:27:29 ·
update #4
He's wearing a blue hat.
C can see A and B, but doesn't know what his hat is. This says that A and B are not both red.
Since C did not know, B knows that his hat or A's hat (or both) is (are) blue. If A had a red hat on, he would know that he had a blue hat himself, and would know the colour of his hat. Since he didn't know, this means A did not have a red hat on and thus had a blue hat.
A did the reasoning that I just did, and knew he had a blue hat.
2006-07-07 13:10:59
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answer #1
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answered by Eulercrosser 4
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So C must see that his buddies are wearing a red cap and blue cap (or 2 blue caps). Leaving a red cap and two blue caps (or 2 red caps and a blue cap) that he might be wearing, he doesn't know which. B knows that he and A are either wearing 1) 2 blue caps or 2) a red cap and a blue cap. He looks at A and crap! He can't tell which means that A is wearing a blue cap, leaving a red or blue for B. A also knows this and can figure, safely, that he is wearing a blue cap. Or maybe I'm just pulling this out of my butt.
2006-07-07 15:26:44
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answer #2
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answered by jerk_strabismus 1
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A knows he has a blue cap.
If both A and B had a red cap, then C would know his cap was blue, but he can't tell, so either A or B or both has a blue cap.
B knows that both he and A cannot have red caps from C's answer. If A's cap was red, then he would know that his was blue. Since he can't answer, A will know he has a blue cap.
2006-07-07 13:11:32
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answer #3
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answered by Anonymous
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I referred to a combination of caps as (A's color, B's color, C's color) abbreviated b = blue and r = red. (example: (b r b) as in A has blue cap, B has red cap, and C has blue cap)
The possible cases are:
(b r b)
if combination was (r r b) C would have known so it is not possible. Therefor A knows his is blue
(b r r)
A knows his is blue
(r b b)
B would have known his is blue this combination is not suitable. B knows that if his was red C would have known the color of his cap so his is not red.
(r b r)
Not possible. B knows
(b b b)
(The hardest one to explain. Hope i make myself clear..) A assumes his is red. in this case C would have not known the color of his cap but at this point B would have figured out that his cap is blue otherwise the combination would have been (r r a) and C would have known. B does not know so A knows his is blue.
(b b r)
A assumes his was red but B would have known his was blue therefor A knows his is not red.
In all possible cases A figures out his is BLUE
2006-07-07 14:08:11
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answer #4
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answered by JinX 2
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A has a blue cap.
Since C didn't know, B knew that either him and A has different colors or both had blue.
B -> "C sees B with blue and A (which B can see). or C sees B with red and A's."
Because of C's answer, we know A and B did not both have Red.
Because of B's answer, we know that A did not have Red since if A had red, B could only have Blue and B did not know his color.
2006-07-07 13:12:43
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answer #5
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answered by Poncho Rio 4
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A has a blue cap--he can see that the other two have red ones.
2006-07-07 13:08:26
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answer #6
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answered by Nelson_DeVon 7
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Blue. If C can't tell, then A+B is 1 or 2 blue. If B can't tell, then A+C=1or2 blue. The only way A can thus know is if both B & C have red hats, thus A must have blue.
2006-07-07 15:00:49
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answer #7
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answered by theanswerer 2
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hi, nice question, pretty simple answer really.
for C to not know what he is wearing combintion must be ONLY (bbb,bbr,brr,brb,rbb,rbr) and NOT (rbb)
now, since C said he doesnt know, B knows now that it its NOT (rbb).
if A had a red hat and B saw this, it would only leave the combination to (rbb) or (rbr) meaning B would know his hat is blue, as b doesnt know what his hat is. i.e b's hat CANT be blue or he would know it was blue
the combination is now (bbb,bbr,brr,brb)
leaving A to only have that hat colour b = BLUE!!!
[plz let me know if i am wrong]
THIS IS PROB THE ANSWER, EXPLAIND IN SIMPLE
2006-07-07 15:30:53
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answer #8
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answered by sk_1808 1
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BLUE
2006-07-07 13:21:08
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answer #9
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answered by stophatinboo 3
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huh?
2006-07-07 13:05:59
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answer #10
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answered by untysteph 2
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