请教各位大牛两道prep数学题

sherylpiao · 发表于 2012-7-10 08:16:37

1. For every positive even integer n, the function h(n) is defined to be the product of all the even integers from 2 to n, inclusive. If p is the smallest prime factor of h(100)+1, then p is?A. between 2 and 10
B. between 10 and 20
C. between 20 and 30
D. between 30 and 40
E. greater than 40

2. For a certain examination, a score of 58 was 2 standard deviations below the mean, and a score of 98 was 3 standard deviations above the mean. What was the mean score for the examination?
A.74 B.76 C.78 D.80 E.82

数学太差，这两题思路都没有，还望各位不吝赐教，先谢过！

jeffery2541 · 发表于 2012-7-10 09:17:53

2·设平均数为X，标注差为Y
58=X-2Y , 98=X+3Y 联立解方程即可（B）
1·这道题我记得以前有过讨论的，等我找找看

linshenzi · 发表于 2012-7-10 09:29:04

1.我记得是h（100）是40以内所有数，inclusive，的倍数，所以加1后就不是那些数的倍数。然后是选E，，依稀记得是这样。。

sherylpiao · 发表于 2012-7-10 13:09:27

原来是这样！太谢谢啦！之前还绞尽脑汁地想怎么用标准差，唉，太笨了。

sherylpiao · 发表于 2012-7-10 13:12:13

1.我记得是h（100）是40以内所有数，inclusive，的倍数，所以加1后就不是那些数的倍数。然后是选E，，依稀记得是这样。。

-- by 会员 linshenzi (2012/7/10 9:29:04)

多谢！我碰到倍数神马的就很头大，多谢解答！

请教各位大牛两道prep数学题

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