JJ56的答案讨论

gmatrico

56. ps 有11個球 6黃5藍, 如果取出後不替換(without replacement) 拿個 1黃1藍的機率有多少

6/11 * 5/10 吧反正有這答案就是了

Guang722(& chen): 确认做法

繁星：without replacement我在这里翻译成“不放回”，那个“不替换”感觉实在是诡异(replacement有“复位”的意思)..如果是不放回，我认为是C(6,1)*C(5,1)/C(11,2)=6/11

我认为应该选6/11

xixiyeye

我也有疑问~请看过的童鞋们赐教~

bilyatp

6/11我觉得第一种解答没有考虑顺序，考虑了之后乘以2就跟第二种解答一样了

孙小北

这个应该是6/11吧

dongfengCA

第一种解法不替换是不是指顺序不变

[此贴子已经被作者于2009/8/2 4:16:32编辑过]

xzhou25

Four possibilities when u r picking the balls.
1: 1st blue, 2nd yellow
2:1st yellow, 2nd blue
3:1st yellow, 2nd yellow
4:1 blue, 2nd blue

The probability of each respective event is
6/11 * 5/10 =30/110
5/11* 6/10= 30/110
5/11 * 4/10 = 20/110
6/11* 5/10=30/110

The first two add up to 6/11, which is the correct answer.