Four wise men are wearing Black and White hats so that each of them can only see the others’ hats.
They are told that at least one of their hats is white and at least one is black.
Asked, in turn, if they can tell the color of their own hat?
The first wise man says no, then the second wise man says no, but then the third wise man could give the right answer.
Answer With Explanation
BWBB, BWWW, BWBW (not ordered)
Now as first person could not tell color of his hat, it means color of other 3 persons hats could be
BWW, BWB (it can’t be all black or all white).
now even the second person can’t tell the color of his hat, color of other 2 persons hats could be
BW (as if it is 2 black or 2 white, he could tell color of his hat, from the previous possibilities).
Now when it is asked from the third person, he can tell color of his hat as opposite to the color of the fourth person hat.