标题: problem on possibility [打印本页] 作者: lisaislisa 时间: 2003-1-19 20:30 标题: problem on possibility
S: teachers, 男女都有，随机挑出2人做某事，问两个都是女老师的概率>1/2吗？
1.女老师的人数>5 2. 两个都是男老师的概率<1/10
答案是B.
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but how come...
[em08] [em08] [em08]
if B
set totally 6 teachers ,two of who are males
the possility of picking two males is 2/6*1/5=1/15 <1/10
while the possility of picking two females is 4/6*3/5=2/5 < 1/2
in another case , let's set totally 100 teachers , two of who are males
the possility of picking two males is 2/100*1/99 <1/10
while the possility of picking two females is 98/100*97/00 >1/2
[em26][em06] [em26][em06] [em26][em06]作者: tongxun 时间: 2003-1-19 23:32
I think that this question may be a incompleted one.作者: lisaislisa 时间: 2003-1-19 23:39
丫头的思路对吗?还有几题要你解答呢
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