prep里的三道数学题，求详解

ashleyker · 发表于 2011-12-7 19:43:25

1、six countries in a certain region sent a total of 75 representatives to an international congress ,and no two countries sent the same number of representatives. of the six countries ,if country A sent the second greatest number of representatives, did country A sent at least 10 representatives ?
(1) one of the six countries sent 41 representatives to the congress
(2) country A sent fewer than 12 representatives to the congress

答案是E

2、a certain city with a population of 13200 is to be divided into 11 voting districts ,and no districts is to have a population that is more than 10 percent greater than the population of any other districts. what is the minimum possible population that the least populated district could have ?
A、10700 B、10800 C、10900 D、11000 E、11100

答案是D、11000

3、the residents of town x participated in a survey to determine the number of hours per week each resident spent watching television . the distribution of the results of the survey had a mean of 21 hours and a standard deviation of 6 hours .the number of hours that

at , a resident of town x , watched television last week between 1 and 2 standard deviation below the mean .which of the following could be the number of hours that Pat watched television last week ?
A、30 B、20 C、18 D、12 E、6

答案是D、12

ashleyker · 发表于 2011-12-7 19:44:00

自己先顶一下。求高人指点！！！多谢了！！！

monica928 · 发表于 2011-12-7 19:58:53

第一个：（1）你用75-41以后得到34 就是说还有5个国家加起来有34 推不出A一定为10
(2)因为不知道最多的有多少，所以也没法确定
两个条件加起来 A也有可能为小于10

第二个：设最少的是X，则其他十个是1.01X, 1.02x,....总之最大不能超过1.10x
求x就是把132000除以这11个数用X表示后得到的表达式，肯定是Ax这种型的，你要求x的最小值，则要求A的最大值，A何时取到最大？当剩下那10个数全部是1.1X的时候，
因此，132000等于12X，x=11000

ashleyker · 发表于 2011-12-7 20:03:15

谢谢！谢谢！！

ashleyker · 发表于 2011-12-7 20:05:13

第三道，求解答

ashleyker · 发表于 2011-12-7 20:14:25

第三道，求解答

hanxulovegmat · 发表于 2011-12-7 20:26:55

between 1 and 2 standard deviation below the mean 我也是这句话没弄懂同求

ashleyker · 发表于 2011-12-7 20:48:21

顶一下

gzchenlu · 发表于 2011-12-7 20:53:04

Average(mean) for the town = 21 h
Standard deviation for the town = 6 h

Pat was between 1 and 2 standard deviations below the mean.

One standard deviation below the mean = Mean - 1*SD = 21 - 6 = 15 h

Two standard deviations below the mean = Mean - 2*SD = 21 - 2(6) = 21 - 12 = 9 h

Therefore, the correct answer (the numbers of hours Pat watched television) lies between 9 and 15 h.

The only correct answer that satisfies that condition is D (12 h).

gaochaoNK · 发表于 2011-12-7 20:56:44

第三题应该是21-12《x《21-6, lz应该去了解一下什么事标准差

prep里的三道数学题，求详解

所属分类: GMAT考试

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