求教几道GWD30数学题

sophialy2008

Q18:

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) %

这题目意思我楞是绕不过来啊，大虾们帮忙啊Q2:

A certain characteristic in a large population has a distribution that is symmetric about the mean m.  If 68 percent of the distribution lies within one standard deviation d
of the mean, what percent of the distribution is less than m + d ?
                                     

A.     16%

B.     32%

C.     48%

D.     84%

E.      92%

这题是无从下手

Q2:

A certain characteristic in a large population has a distribution that is symmetric about the mean m.  If 68 percent of the distribution lies within one standard deviation d
of the mean, what percent of the distribution is less than m + d ?
                                     

A.     16%

B.     32%

C.     48%

D.     84%

E.      92%

这题是无从下手

Q29:

The toll for crossing a certain bridge is $0.75 each crossing.  Drivers who frequently use the bridge may instead purchase a sticker each month for $13.00 and then pay only $0.30 each crossing during that month.  If a particular driver will cross the bridge twice on each of x days next month and will not cross the bridge on any other day, what is the least value of x for which this driver can save money by using the sticker?



A.     14

B.     15

C.     16

D.     28

E.      29

Q4:

If the average (arithmetic mean) of positive integers x, y, and z
is 10, what is the greatest possible value of z ?


A.     8

B.     10

C.     20

D.     28

E.      30



貌似有点多， 请求各位高手帮我看看把

不胜感激啊

zzloveyibo

sayysong 发表于 2009-11-14 14:59
第二题 DA certain characteristic in a large population has a distribution that is symmetric about th ...

大神啊。。。我终于懂了。。。看了这么多的帖子，，，就这个最明白了。。。

ZXJun

是D吧。

sophialy2008

第二题 D
A certain characteristic in a large population has a distribution that is symmetric about the mean m.  If 68 percent of the distribution lies within one standard deviation d of the mean, what percent of the distribution is less than m + d ?
题目说围绕平均值m做对称分布，有68%的分布在平均值周围(左右两边)标准方差为d的范围内，其实说的范围是 [m-d, m+d]。
现在要求的是[... , m+d]范围内的百分比。
画个数轴就知道了，分布在 [m-d, m+d]以外的是 1-68%=32%，左右各16%，再16%+68% = 84%。

-- by 会员 sayysong (2009/11/14 14:59:32)

呼呼， 偶明白了， 还是概率的问题啊， 挺深奥的，谢谢解答

sayysong

后面两题大家手都快，热心人好多啊～ 我也同意大家的看法。

sayysong

第二题 D
A certain characteristic in a large population has a distribution that is symmetric about the mean m.  If 68 percent of the distribution lies within one standard deviation d of the mean, what percent of the distribution is less than m + d ?
题目说围绕平均值m做对称分布，有68%的分布在平均值周围(左右两边)标准方差为d的范围内，其实说的范围是 [m-d, m+d]。
现在要求的是[... , m+d]范围内的百分比。
画个数轴就知道了，分布在 [m-d, m+d]以外的是 1-68%=32%，左右各16%，再16%+68% = 84%。

sophialy2008

Q4 是28吧
x、y、z=positive integers

x+y+z=30    Zmax=28  x=y=1

-- by 会员 heavennancy (2009/11/14 14:53:51)

啊 原来是这样 看来我理解有问题啊，

heavennancy

Q4 是28吧
x、y、z=positive integers

x+y+z=30    Zmax=28  x=y=1

sophialy2008

#18  D
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?
设原来的每股价格是P，原来的每股收益是E，那么原来的每股价格/每股收益为 r1 = P/E
现在每股价格涨了k%，即（1+k%）P，现在的每股收益为（1+m%）/E，现在的每股价格/每股收益为 r2 = （1+k%）P/（1+k%）M
要求的是increase的ratio，即 （ r2 - r1 ） / r1 = ( k - m ) / ( 100 + m)，做一下百分比换算，就得到D了。

-- by 会员 sayysong (2009/11/14 14:50:30)

谢谢大牛们 呵呵

sayysong

#18  D
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?
设原来的每股价格是P，原来的每股收益是E，那么原来的每股价格/每股收益为 r1 = P/E
现在每股价格涨了k%，即（1+k%）P，现在的每股收益为（1+m%）/E，现在的每股价格/每股收益为 r2 = （1+k%）P/（1+k%）M
要求的是increase的ratio，即 （ r2 - r1 ） / r1 = ( k - m ) / ( 100 + m)，做一下百分比换算，就得到D了。