智力快車

三位旅行者誤入一片叢林，被食人族抓獲。食人族給了他們一個逃生的機會。他們把這三個人綁在木樁上排成一條線，最后面的人能看到前面兩個人的背部，中間的人只能看到他前面那個人的背部，而最前面的人誰也看不到。然后給這三個人看了五頂帽子，三頂黑色的。兩頂白色的。

接著，食人族把這三個人的眼睛蒙上，在他們每個人頭上放了一頂帽子。藏起剩余的兩頂帽子，然后把蒙著這三個人眼睛的布條松開，告訴他們只要一個人猜出自己頭上戴的是什么顏色的帽子，他們就都可以走。而如果猜錯了，他們三人都將被處死。時間一分分過去，最后，最前面的那個誰也看不到的人正確地猜出了自己帽子的顏色。請問他戴的是什么顏色的帽子?他是怎么猜到的?

Answer：

The back man could see the hats wornby the two men in front of him．So．if both ofthose hats were white．he would know that thehat he wore was black.But．since he didn’tanswer．he must have seen at least One blackhat ahead of him．

After it became apparent to the middleman that the back man couldn't figure outwhat he's wearing．he knew that there was atleast one black hat worn by himself and thefront man．

Knowing this，if the middle man saw awhite hat in front of him．he'd know that his own hat was black．and could answer the question correctly．But，since he didn't answer，he must have seen a black hat on the frontman．

After it became apparent to the front man that neither of the men behind him could answer the question．he realized the middle man saw a black hat in front of him．So he Said，也correctly，“My hat is black.”