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I have got a puzzle that I wanted to share.

In a quiz show, three candidates were shown five slips of paper - three white and two black. Then they were blindfolded and one of the slips of paper was pasted on each of their foreheads. After removing the blindfolds, it was explained that the first person to guess the color of their slip of paper would win. Since all had white slips of paper on their foreheads, the candidates were at first at a loss. After some time, however, all three came up with the correct solution almost simultaneously. What thinking had they done?

Of course, they don't talk to each other or look at their own piece of paper. No one is cheating and it is a logic puzzle, not a trick question.

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  • $\begingroup$ I assume it's not in the spirit of the puzzle for them to take the paper off their foreheads and look at them? $\endgroup$
    – The Empty String Photographer
    Jul 31 at 18:39
  • $\begingroup$ @TheEmptyStringPhotographer No, good that you mention it. $\endgroup$
    – calculatormathematical
    Jul 31 at 19:16

1 Answer 1

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Call the people A, B, and C.

A thought "If I have black then B is thinking 'If I have black then C knows he's got white. But C is being silent so I must not have black' but B is being silent so I must not have black." And the others thought the same way, mutatis mutandis.

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