考试在即，真诚求助几道数学题，请各位同学帮助解答，多谢！

rainny0906 · 发表于 2011-4-24 12:22:54

1、for a certainn examination, a score of 58 was 2 standard deviation below the mean, and a scorre of 98 was 3 standard deviations above the mean. what was the mean score for the examination
74/76/78/80/82(答案是74)

2、a certain library assesses fines for overdue booking as follows. on the first day that a book is overdue, the total fine is $0.10, for each additional day that the book is overdue, the total fine is rither increased by $ 0.30 or doubled, whichever results in the lesser amount. what is the total fine for a book on the fourth day it is overday?
0.60/0.70/0.80/0.90/1(答案是0.70)

3、on a certain sight-seeing tour, the ratio of the number of women to the children was 5 to 2, what was the number of men on the sight-seeing tour?
(1)on the sight-seeing tour, the ratio of the number of children to the number of men was 5 to 11
(2)the number of women on the sight-seeing tour was less than 30
答案：both statements together are sufficient , but neither statemnet alone is sufficient.

4、the ratio of a certain chemical reaction is directly proportional to the square of the concentration of chemical A present and inversely proportional to the concentration of chemical B present. if thr concentration of chemical B is increased by 100 percent, which of the following is closest to the percent change in the concentration of chemical A required to keeo the reacion rate unchanged.
(1)100% decreased (2)50%decreased (3)40decreased (4)40%increased (5)50%increased
答案（4）

5、if x的4次方+y的4次方=100，then the greatest possible value of X is between
(1)0 and 3 (2)3and 6 (3)6 and 9 (4)9and 12 (5)12 and 15
答案（2）

6、last month 15 homes wew sold in town X, the average (arithmatic mean) sale price of the homes was $150000, and the median sale price was $130000. which of the following statements must be true?
(1)at least one of the homes was sold for more than $165000
(2)at least one of the homes sold for more thant $130000 and less than $165000
(3)at least one of the homes sold for less than $130000
答案（1）

vikinghui · 发表于 2011-4-24 21:10:15

这是楼主做Prep的题吧，3，4，6我也遇到了

1.题目说58比平均数少2个标准差，98比平均数多3个标准差，所以标准差就是（98-58）/（3+2）=8，平均数等于58+8*2=74

2.第一天费用0.1，第二天0.1*2=0.2，第三天0.2*2=0.4，第四天0.4+0.3=0.7

3.根据条件一得女人；小孩：男人=25：10：22，条件二又说女人少于30，那就是25了，男人就是22了

4.题目说这个反应速率和A的浓度的平方成正比，和B浓度成反比，就是r=cA^2/B，c为常数，那B增加了100%就是double了，设A变为原来的xA，公式变成r=c（xA）^2/2B，把几个答案代进去算一下就可以了

5.3^4=81<100，4^4=256>100，题目没说x是整数，那就在3到4中间了

6.
1）题目说中位数是130000，那么至少有一半是小于等于这个数，而平均数是150000，假设没有一套房子超过165000，那么它们的平均数最多不超过（130000*8+165000*7）<150000
2)不一定，因为（130000*8+165000*7）<150000，所以就算130000以上的另外7套房子都超过165000也是可以的
3）不一定，可以有8套都是130000啊

rainny0906 · 发表于 2011-4-24 23:24:07

解答得非常详细呀，赞一个，多谢。

考试在即，真诚求助几道数学题，请各位同学帮助解答，多谢！

所属分类: GMAT考试

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