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标题: 再求两题~谢谢了~数学啊...... [打印本页]

作者: Avatar800 时间: 2010-6-30 00:54
标题: 再求两题~谢谢了~数学啊......

Last year the price per share of Stock X increased by k percent and the earnings per share of Stock X increased by m percent, where k is greater than m.By what percent did the ratio of price per share to earnings per share increase, in terms of k and m?

A.k/m %
B.(k-m) %
C.[100(k-m)]/(100+k) %
D.[100(k-m)]/(100+m) %

E.[100(k-m)]/(100+k+m) %

这个应该怎么弄呢？？

On Saturday morning, Malachi will begin a camping vacation and he will return home at the end of the first day on which it rains.If on the first three days of the vacation the probability of rain on each day is 0.2, what is the probability that Malachi will return home at the end of the day on the following Monday?

A.0.008
B.0.128

C.0.488
D.0.512
E.0.640
呃~~这个题没看明白什么意思~

作者: keith139 时间: 2010-6-30 01:42
第一个还行，未上涨之前的设为P1,E1;上涨之后的设为P2,E2;由题意得出P2=(1+K)P1,E2=(1+M)E1;比率的变化可以写成(P2/E2-P1/E1)/(P1/E1);之后将前边的两个式子替换进去，将相同的部分消了就有了。

作者: passiona 时间: 2010-6-30 01:52
No.2
M returns on Monday = no rain on sat & sun, rain on monday

P=(1-0.2)(1-0.2)*0.2

作者: Avatar800 时间: 2010-6-30 10:28

No.2
M returns on Monday = no rain on sat & sun, rain on monday

P=(1-0.2)(1-0.2)*0.2

-- by 会员 passiona (2010/6/30 1:52:25)

呃~~~~~有点晕~拜托能再解释下么？M returns on Monday = no rain on sat & sun, rain on monday 怎么推出这个等式的？？谢谢了

作者: savageprince 时间: 2010-6-30 10:34

No.2
M returns on Monday = no rain on sat & sun, rain on monday

P=(1-0.2)(1-0.2)*0.2

-- by 会员 passiona (2010/6/30 1:52:25)

呃~~~~~有点晕~拜托能再解释下么？M returns on Monday = no rain on sat & sun, rain on monday 怎么推出这个等式的？？谢谢了

-- by 会员 Avatar800 (2010/6/30 10:28:05)

要想Return on Monday, 必须Sat, Sun都不下雨, 而且Mon一定要下雨, Sat和Sun不下雨的概率是0.8 (1-0.2), Mon下雨的概率是0.2, 所以就推出这个等式啦~

作者: Avatar800 时间: 2010-6-30 10:36

第一个还行，未上涨之前的设为P1,E1;上涨之后的设为P2,E2;由题意得出P2=(1+K)P1,E2=(1+M)E1;比率的变化可以写成(P2/E2-P1/E1)/(P1/E1);之后将前边的两个式子替换进去，将相同的部分消了就有了。

-- by 会员 keith139 (2010/6/30 1:42:21)

偶也是这么算的啊~就是弄不出来它那个结果..分母(100+m) 应该是1+m吧?

作者: Avatar800 时间: 2010-6-30 10:38

No.2
M returns on Monday = no rain on sat & sun, rain on monday

P=(1-0.2)(1-0.2)*0.2

-- by 会员 passiona (2010/6/30 1:52:25)

呃~~~~~有点晕~拜托能再解释下么？M returns on Monday = no rain on sat & sun, rain on monday 怎么推出这个等式的？？谢谢了

-- by 会员 Avatar800 (2010/6/30 10:28:05)

要想Return on Monday, 必须Sat, Sun都不下雨, 而且Mon一定要下雨, Sat和Sun不下雨的概率是0.8 (1-0.2), Mon下雨的概率是0.2, 所以就推出这个等式啦~

-- by 会员 savageprince (2010/6/30 10:34:32)

啊~~~~~~~~我没脑了~~~~~~~呵呵，多谢

作者: keith139 时间: 2010-6-30 10:48

-- by 会员 keith139 (2010/6/30 1:42:21)

偶也是这么算的啊~就是弄不出来它那个结果..分母(100+m) 应该是1+m吧?

-- by 会员 Avatar800 (2010/6/30 10:36:47)

后边不是带着百分号呢么？？呵呵

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