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标题: 请教两道PREP的MATH [打印本页]

作者: delia716 时间: 2006-10-23 08:56
标题: 请教两道PREP的MATH

第一题就没看懂

1. The arithmetic mean and standard deviation of a certain normal distribution are 13.5 and 1.5, respectively, what value is exactly 2 standard deviations less than the mean?

A) 10.5 B) 11.0 C) 11.5 D)12.0 E) 12.5

answer is A)

2. Five pieces of wood have an average (arithmetic mean) length of 124cm, and a median leghth of 140cm. What is the maxium poosible length, in centimeters, of the shortest piece of wood?

A) 90 B) 100 C) 110 D) 130 E) 140

answer is (B)

Thank you very much

作者: floridaus 时间: 2006-10-23 11:04
2, (a+b+c+d+e)/5=124, respectly, c=140, then if hope a(the shortest piece of wood)is maxium, then d and e must as short as possible d=e=140, then a=b=100

作者: irisyuzh 时间: 2006-10-23 11:13

题目出的玄乎又玄,BS米国人,其实就是简单的加减法:

13.5-1.5*2=10.5

作者: delia716 时间: 2006-10-23 13:02

以下是引用floridaus在2006-10-23 11:04:00的发言：
2, (a+b+c+d+e)/5=124, respectly, c=140, then if hope a(the shortest piece of wood)is maxium, then d and e must as short as possible d=e=140, then a=b=100

thank you . thank you!!!

作者: delia716 时间: 2006-10-23 13:03

以下是引用irisyuzh在2006-10-23 11:13:00的发言：

题目出的玄乎又玄,BS米国人,其实就是简单的加减法:

13.5-1.5*2=10.5

我的天哪，难道就是这个意思。难怪第一道呢，我还花了5分多种愣没傻哪了

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