[求助]请教几道数学题(有JJ，有GWD)

danalau

1# GWD31-15 Q28

A school administrator will assign each student in a group of n students to one of m classrooms.  If 3 < m < 13 < n, is it possible to assign each of the n students to one of the m classrooms so that each classroom has the same number of students assigned to it?

(1)   It is possible to assign each of 3n students to one of m classrooms so that each classroom has the same number of students assigned to it.

(2)   It is possible to assign each of 13n students to one of m classrooms so that each classroom has the same number of students assigned to it.

完全不知道它在说什么！！！麻烦给解释一下，多谢！

2#  A department manager distributed a number of pens, pencils, and pads among the staff in the department, with each staff member receiving x pens, y pencils, and z pads.  How many staff members were in the department ?

(1)   The numbers of pens, pencils, and pads that each staff member received were in the ratio 2 : 3 : 4, respectively.

(2)     The manager distributed a total of 18 pens, 27 pencils, and 36 pads.

这题我选C，答案是E。

好像应该是有机关吧，但是我看不出来。

3#   For what percent of those tested for a certain infection was the test accurate; that is, positive for those who had the infection and negative for those who did not have the infection?

(1)     Of those who tested positive for the infection,  did not have the infection.

(2)     Of those tested for the infection, 90 percent tested negative.

答案是E，我选的是C。

我是想，90%negative，说明10%positive，10%里又有1/8是不infection的，那不就能算出来是有10%*7/8是infection的吗？

4#   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

5# JJ 129、ds 0<x<1, 问 nonzero tenth =?

    1) 16x=整数

2）8x=整数

bigur解答：1) x＝n/16  n<16 取整数
                无法判断

           2) x=m/8  m<8 取整数  无法判断

记得之前有一道一样的题，好像上次说（2）可以，因为1除以8等于0.125，所以tenth是1。有点晕。

6# 问一个说法，说某点“在圆上”（即在圆周上）或者是“在圆内”都分别怎么表述？我有两次因为这个做错题。

 

k_wang_2008

1.题意就是说m能否被n整除.(1)说m能被3n整除,(2)说m能被13n整除.这题我选B.

2.给你举反例吧.两人6,9,12),(12,18,24).三人:分别都是(6,9,12).存在多于一种可能性,因此选E.

3.令被检测的人的集合为全集R,感染的人的集合是A,呈阳性的人的集合是B,你求出的是A交B占全集的百分比,而题目问的是是否可以求出A交B与(R-A)交(R-B)的并集占全集的百分比.(1)(2)联立仍旧无法求出检测呈阴性的人里到底有多少是未被感染的,所以选E.

4.我选E.因为2*4*6*...*100+1这个数被任何一个2至47之间(含)的质数除都必然余1,所以它最小的质因子必大于47,也就大于40.

5.那2除以8还得0.25呢...

1,4两题你可以再对答案加以验证.

[此贴子已经被作者于2009-6-29 0:50:20编辑过]