題目網址: http://www.puzzleup.com/2016/
http://www.puzzleup.com/2016/puzzle/?16
答題時限: 11月10日7PM-比賽結束(約12月14日)
加分時限: 11月10日7PM-11月16日6:59PM
答對可得基本分100分。答案可上傳5次,每改1次答案從基本分扣20分。
比賽期間內可隨時上傳答案,加分時限內答對第n天加(6-n)分
另依題目的難易有額外加分(如有80%的人這題答錯,答對者加80分)
◆FIVE NUMBERS
Five numbers are selected randomly between 1 and 100 (1, 2, ..., 99, 100). If
the selected numbers are all different and their sum is equal to 100, the
smallest number is noted. If this process is repeated many times, what would
be the average of the noted numbers?
Note: All numbers have the same probability of selection.
Enter your answer as a simplified fraction. Example:12/23
由 1 至 100 中均勻隨機選取五個數。
若此五數互不相同且其總和恰為 100, 則記下此中最小的數字。
重覆此操作許多次後,所記下數字的平均為何?
以最簡分數回答,如 12/23。