请教prep数学题。。。

xiaomakunkun

RT   在下数学真心弱。。。见笑了。。。望各位NN不吝赐教。。~  拜谢~
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
答案是E。。。   

2.According to the directions on a can of frozen orange juice concentrate. 1 can of concentrate is to be mixed with 3 cans of water to make orange juice. How many 12-ounce cans of the concentrate are required to prepare 2006-ounce services of orange juice?   
答案是25.。。   但是我怎么算都是40上下、。。纠结

3. The residents of Town X participated in a survey to determine the number of hours per week each resident spent watching televition. The distribution of the survey had a mean of 21 hours and a standard deviation of the survey had a mean of 21 hours and a standard deviation of 6 hours. The number of hours that Pat, a resident of Town X, watched televition last week was 1 and 2 standard deviation below the mean.(这句话看得不是很懂。。) Which of following could be the hours Pat watched TV last week?
A.30     B.20      C.18      D.12      E.6     
答案是D.12
4. x,y,z 都是大于1 的整数，求X+Y+Z? (DS题)
a.xyz=70
b.(x/yz)=(7/10)

答案选的A。。  这这。。

以上。。求NN解答。。感激不尽啊。。

xiaomakunkun

明白了~    太感谢啦！！

wanghonglia

第4题：
(a) xyz=70=2*5*7
x，y，z必然是2、5、7中的某一个，不管具体值如何x+y+z=14

所以(a)充分

wanghonglia

对的，而且有below说明在均值下面

xiaomakunkun

所以 between 1 and 2 standard deviation 是标准差的一倍到两倍的意思吗？。。。

wanghonglia

第三题题目表述也错了，应该是“The number of hours that Pat, a resident of Town X, watched television last week was between 1 and 2 standard deviations below the mean.” 差了between会害死人的。
所以答案应该在9(=21-2*6)和15(=21-6)之间

xiaomakunkun

这个。。为什么是200*6？    所以题目是说200份6盎司的果汁吗？。。

wanghonglia

第二题：浓缩液concentrate和juice的比例为1:4，设需要X
列式：12*X*4=200*6 => X=25

原题是“ 200个6-Ounce servings of orange juice”而不是“2006-Ounce servings of orange juice”，难怪你解不出来。