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3道数学题,麻烦各位帮我看看

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楼主
发表于 2009-2-26 10:34:00 | 只看该作者

3道数学题,麻烦各位帮我看看

Q25:
A photographer will arrange 6 people of 6 different heights for photograph by placing them in two rows of three so that each person in the first row is standing in front of someone in the second row.  The heights of the people within each row must increase from left to right, and each person in the second row must be taller than the person standing in front of him or her.  How many such arrangements of the 6 people are possible?

A.    5
B.    6
C.    9
D.    24
E.    36

答案 是a 为什么?

Q30:
Joanna bought only $0.15 stamps and $0.29 stamps.  How many $0.15 stamps did she buy?
(1)      She bought $4.40 worth of stamps.
(2)      She bought an equal number of $0.15 stamps and $0.29 stamps.
   
A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.

答案是d 为什么?


Q35:
What is the median number of employees assigned per project for the projects at Company Z?
(1)    25 percent of the projects at Company Z have 4 or more employees assigned to each project.
(2)     35 percent of the projects at Company Z have 2 or fewer employees assigned to each project.
   
A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.

答案是c 为什么?

感谢各位的帮助!!

沙发
发表于 2009-2-26 16:22:00 | 只看该作者

Q.25

思路:用1-6代表身高。1和6的位置是固定的。而5要么在6的下面,要么在6的左边。总共5种情况:

第二排:2,4,6     3,4,6    4,5,6    2,5,6    3,5,6

第一排:1,3,5     1,2,5    1,2,3    1,3,4    1,2,4


[此贴子已经被作者于2009-2-26 16:23:05编辑过]
板凳
发表于 2009-2-26 16:39:00 | 只看该作者

Q30.

答案有误。应该选A。

(2)不充分。两种邮票可以各买1张,也可以各买10张,只要数量相同即可。$4.4是(1)中条件.

(1)充分。

设15x+29y=440

5与自然数相乘,尾数为5或者0。

9与自然数相乘,尾数为9-1中的任何一个数。

因为440的尾数是0,所以y的尾数必须是5或者0。

             y                         x

440-29* 5=295=15*x    非整数

440-29*10=150=15*x      10

440-29*15= 5 =15*x    非整数


[此贴子已经被作者于2009-2-26 16:43:19编辑过]
地板
发表于 2009-2-26 16:53:00 | 只看该作者

456

356

256

246

346

123

124

134

135

125

看到题目可以先列式à0.15x+0.29y

1)      0.15x+0.29y=4.40à思维过程是,因为0290.15两个小数后面是59,然后观察到总数为4.40,所以0.150.29应该是一个10的整数的个数张,否则不会凑到4.40,所以可以从10开始试,就是0.15*10+0.29*10=4.40—》确定,所以得解

她买了相同数量的0.290.15à无法推断出结果。故此我觉得答案应该是A,这种题型好像在涛涛上很多

先理解MEDIAN,就是假设100个人,就是5051的人。

135%的人是2个人或者更少

45%中间是派2<x<4,

X肯定是个数,则为3

2)25%的人是4个人或者更多

5#
发表于 2009-2-26 16:54:00 | 只看该作者

Q35.

(1)(2)各自都不充分。

(1)+(2)得出下表:

35%

40%

25%

1,2

3

4,5,……

中数显然落在3这个位置。

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