求助!GWD-14中的2和11题，都是DS题，很困惑！！在线等，求大家帮忙！！

yvonnechen88

2.If 2 different representatives are to be selected at random from a group of 10 employees and if p is the probability that both representatives selected will be women, is p >1/2?
(1)More than 1/2 of the 10 employees are women.
(2)The probability that both representatives selected will be men is less than1/10

这个题的答案是什么啊？？有说是B有说是E的，麻烦大家给我个解释和统一答案吧？？





11.Mary persuaded n friends to donate $500 each to her election campaign, and then each of these n friends persuaded n more people to donate $500 each to Mary’s campaign.If no one donated more than once and if there were no other donations, what was the value of n?
(1)The first n people donated  1/16  of the total amount donated.
(2)The total amount donated was $120,000.

第一个条件肯定能推出来n值，可是第二个的确是能通过一个二次方程计算出来，但是n不是一个正整数，人数必须是正整数啊！！这样的话第二条件肯定是不行的啊！！
求牛人点拨，在线等！！！

yvonnechen88

说的更清楚些。
500n+500n^2=120000
即n+n^2=240
n=15或n=-16（舍）
楼主再算一下吧，耐心些，不要着急~

-- by 会员 fanchuanqi (2010/4/26 19:55:49)

哇塞，一下子明白了~~~感谢你哈~~~

fanchuanqi

说的更清楚些。
500n+500n^2=120000
即n+n^2=240
n=15或n=-16（舍）
楼主再算一下吧，耐心些，不要着急~

fanchuanqi

同意。11题选D

轩辕gossip

第二题选D，n^2+n=240，n=15

yvonnechen88

我也觉得11题就是选A，答案应该是错了吧~~

windypig123

囧。我说的第二个题。。11题。。不是2

RedDevils

11题A?

windypig123

第二题选A吧。不知道答案选啥。。。2算不出整数娃

RedDevils

第一题，先用不等式估算（2）吧
得出Female>=7
然后代入，3男7女，p=7*6/(10*9)<1/2
答案E