[Puzzle: Can you help 10 students get A+?]【謎題:你能幫這十個學生拿到A+ 嗎?】

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[Puzzle: Can you help 10 students get A+?]

By: DUAN Yanlin, Alan (Jockey Club Academy Hall)
Image: http://www.emrgnet.eu/

Feeling sleepy and tired in this busy week? Burning night oil because of your finals preparation? How about trying out an interesting puzzle together to make your brain back to work?

10 students are taking an unusual GE course. Every day, the teacher will randomly invite one student entering into a room, in which a coin was put on the desk, initially with its head up. In the room, the student can only choose to do (or not do) two things: 1) choose to flip the coin or not; 2) claim that all 10 students have been to this room by now. If he/she is wrong, then the game is over immediately and all students will fail this course. If he/she is right, then all 10 students will get A+. Due to academic integrity, no one can talk to each other anymore once the course starts and no one can see the coin unless they are in the room. The question is: if the 10 students are allowed to come up with a strategy together before the course officially starts, what their plan would be so that all of them can finally get an A+?

Feel free to leave your thoughts and answers at the bottom of this page. It is also welcomed to share this article together with your ideas to Facebook or Weibo with tag #ResLinkBrainTeaser. We will post the solution very soon!

Happy puzzle solving!

Puzzle adapted from: http://www.cut-the-knot.org

【謎題:你能幫這十個學生拿到A+ 嗎?】

文: 段延麟 (賽馬會群智堂)
圖: http://www.emrgnet.eu

忙碌了一週感覺疲倦不已、睡意昏沈?挑燈夜戰只為複習期末考試?一起做到腦筋急轉彎,來體驗一下腦力激盪吧!

十個學生正在上一門與眾不同的通識教育課。每天,老師都會邀請一名學生進入到一間「密室」。密室裡有一枚硬幣,一開始正面朝上。在房間裡,學生只可以選擇做(或者不做)兩件事情:一,翻轉硬幣;二,選擇告訴老師所有十位同學都已經進入過這個房間。如果他/她這麼說了,但實際上並非所有同學都曾進入過,那麼遊戲結束,所有同學這門課均不通過。但如果他/她是對的,那麼遊戲也結束,十名同學都可以獲得A+。出於學術誠信的角度考慮,一旦這門課開始了,所有學生就不得與其他人交流。另外,除了進到房間裡,否則沒有別的方式可以知道當前硬幣哪一面朝上。那麼問題來了:如果十名同學可以在課程正式開始之前商量對策,那麼怎樣的計畫可以保證他們所有人都拿到A+呢?

如果你有什麼想法或者已經想到答案,就快快在本文下方留言吧。也歡迎你將這篇文章和你的想法分享到臉書或微博平台並使用標籤#ResLinkBrainTeaser。答案很快公佈!

解題愉快!

謎題改編自:http://www.cut-the-knot.org

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