THE MISSING DOLLAR

原文

The missing dollar riddle is a famous riddle that involves an informal fallacy. It dates back to at least the 1930's, although similar puzzles are much older.
Although the wording and specifics can alter, the puzzle runs along these lines:
Three people check into a hotel room. The clerk says the bill is $30, so each guest pays $10. Later the clerk realizes the bill should only be $25. To rectify this, he gives the bellhop $5 to return to the guests. On the way to the room, the bellhop realizes that he cannot divide the money equally. As the guests didn't know the total of the revised bill, the bellhop decides to just give each guest $1 and keep $2 as a tip for himself. Each guest got $1 back, so now each guest only paid $9, bringing the total paid to $27. The bellhop has $2. And $27 + $2 = $29 so, if the guests originally handed over $30, what happened to the remaining $1?

解讀

Fallacy 謬誤。
一般是指思路上的錯(cuò)誤或者不當(dāng)?shù)倪壿嬐评怼?br> 例句：It was once a popular fallacy that the world is flat.
這種謬誤又分兩種, formal 和 informal.
Formal fallacy 指的是推理結(jié)構(gòu)本身的錯(cuò)誤。
Informal fallacy 是不當(dāng)?shù)倪壿?，易誤導(dǎo)的言辭，混亂的思路引起的錯(cuò)誤。
你覺得上面這個(gè)例句的謬誤是屬于formal 還是 informal 呢？
當(dāng)然這種謬誤都不是有意的。如果是蓄意的，惡意的，在中文里我們稱之為詭辯， 相應(yīng)的英語(yǔ)是sophism.
Bellhop 旅館侍者。
旅館的前臺(tái)一般都有一個(gè)鈴鐺（bell）, 當(dāng)你按鈴的時(shí)候就有人（跳，jump, hop）出來(lái)為你服務(wù)。
有很多的職業(yè)的名字都很好玩， 比如
Busser: 餐館或咖啡廳收拾桌子的人
Honey Dipper: 鉆下水道井蓋的維修工人（戲稱）
Chick Sexer: 分辨小雞性別的人
Eggler: 買賣雞蛋的商人
Hairapist: 美發(fā)治療師。理發(fā)師給人理發(fā)很多年了， 聽了很多八卦，于是可以一邊理發(fā)， 一邊給人提供建議和生活的哲理的人。這個(gè)詞應(yīng)該是Hair-stylist 美發(fā)師和 Therapist 心理醫(yī)師的合體。

答案

這個(gè)puzzle犯的邏輯錯(cuò)誤是把收入和支出混在一起了。一個(gè)好的會(huì)計(jì)（accountant）會(huì)把賬本分開算。

旅店收了$30元退了$5元，收入為$25元。
侍者$5元只還了$3元，往自己包里放了$2元。收入為$2元。
目前為止總收入為$27.
三個(gè)客人共出了$30元， 但是每人又收回$1（$1x3=$3）元，總共支出為$27元。
收入和支出相等，所以并沒有錢流失。