推 APM99 :2. 你把他翻譯成中文你就知道了 10/16 17:38
※ [本文轉錄自 Grad-ProbAsk 看板 #1GVGbuNS ]
作者: KAINTS (RUKAWA) 看板: Grad-ProbAsk
標題: [理工] 機率
時間: Tue Oct 16 15:14:57 2012
1.
A ordinary deck of 52 cards is dealt,13 each,at random
among A,B,C,and D.Waht is the probability that A and
B together get two aces?
我一開始是算4C1*48C12*3C1*36C12/52C13*39C13
但解答給的是4C2*48C24/52C26
為什麼他是一起考慮???是因為"together"這單子嗎??
A and B一起取這樣??
2.
From the set of all families with two children,(a)a family is selected
at ranndom and is found to have a girl,what is the prob. that the
other child of the family is a girl?,(b) a child is selected at random
and is found to be a girl,what is the prob. that the second child of
this girl's family is also a girl? Assume that in a two-child family
all sex distributions are equally probale.
答案分別是(a) 1/3,(b) 1/2
想請問一下這兩題問的差異在哪裡?
--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 111.70.247.44
※ 編輯: KAINTS 來自: 111.70.247.44 (10/16 15:57)
※ 發信站: 批踢踢實業坊(ptt.cc)
※ 轉錄者: KAINTS (111.70.247.44), 時間: 10/16/2012 15:58:58