[讨论]天山6-9

rengangjhq

Q9:
A gardener is going to plant 2 red rosebushes and 2 white rosebushes.If the gardener is to select each of the bushes at radom,one at a time,and plant them in a row, what is the probability that the 2 rosebushes in the middle of the row will be the red rosebushes?
A1/12
B1/6
C1/5
D1/3
E1/2
In my opinion,由于同一种颜色的花不可分,从2红2白中选四花种的选择有:    红白白红,红白红白,红红白白
        白红红白,白红白红,白白红红
2 rosebushes in the middle of the row will be the red rosebushes 有两个,
所以概率为1/3
请赐教

beautywawa

以下是引用rengangjhq在2005-1-13 21:02:00的发言：

Q9:
A gardener is going to plant 2 red rosebushes and 2 white rosebushes.If the gardener is to select each of the bushes at radom,one at a time,and plant them in a row, what is the probability that the 2 rosebushes in the middle of the row will be the red rosebushes?
A1/12
B1/6
C1/5
D1/3
E1/2
In my opinion,由于同一种颜色的花不可分,从2红2白中选四花种的选择有:    红白白红,红白红白,红红白白
        白红红白,白红白红,白白红红
2 rosebushes in the middle of the row will be the red rosebushes 有两个,
所以概率为1/3
请赐教

幾有一種,,,ANS:1/6

rengangjhq

这么简单都搞错了

看来我今天有点不正常了

[此贴子已经被作者于2005-1-13 21:13:58编辑过]

Pudding

請問一下這題如果是要用公式計算要怎麼算呢?

[此贴子已经被作者于2005-2-28 11:49:42编辑过]

swimmingfrog

这道题是不是这样算：C4^3/C4^4=1/6

就是把2个rosebushes 当作一个，然后再组合？

hhnelson

In my opinion,由于同一种颜色的花不可分,从2红2白中选四花种的选择有:    红白白红,红白红白,红红白白
        白红红白,白红白红,白白红红

题目没说由于同一种颜色的花不可分??

我是这样的: P(2,2)P(2,2)/P(4,4) 或者2/4*2/3*1/2*1=1/6

andrew_li

题目没说由于同一种颜色的花不可分

It does not matter. The outcome would be the same on either case.