马上考了，问GWD里几道题

yifeifan

红色的是正确答案。

On a certain transatlantic crossing, 20 percent of a ship’s passengers held round-trip tickets and also took their cars abroad the ship.  If 60 percent of the passengers with round-trip tickets did not take their cars abroad the ship, what percent of the ship’s passengers held round-trip tickets?

 

A.      33 1/3%

B.       40%

C.      50%

D.      60%

E.       66 2/3%
我遇到这类题从来没做对过！完全不知道怎么入手（不知道怎么形容这类题目，反正就是象N个人有male/female，又分别有A/B特征，各占多少百分比……），唉找不到合适的例子了。
有理解的同学能帮帮忙指点一下吗？我遇到这类混合的题根本没思路。。。

Q10:

A set of numbers has the property that for any number t in the set, t + 2 is in the set.  If –1 is in the set, which of the following must also be in the set?

 

I.                    -3

II.                  1

III.                5

 

 

A.    I only

B.    II only

C.    I and II only

D.    II and III only

E.    I, II, and III

我当时选的Answer: E
为什么没有-3？我记得初中时候学映射的时候做过这类题。当T+2=-1时，T=-3可以在集合中啊！

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. 我选的是A

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.

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
这个题目不理解。
谢谢！

[此贴子已经被作者于2009/9/22 15:07:17编辑过]

sysxy1987

1.从题目中可以看出那些有round-ticket且带car的应该占了round-ticket的40%，那么round-ticket就应该是20/40=50%

2.这个题目的推理只能往上推，不能往下推，没有说t在，t-2在，只能往上推。

3.第一种你仔细算下，只有一种可能就是两个都是10.没别的组合了！

4、假设从小到大是ABCDEF

那么第一排第一个之能是A，而第二排最后一个只能是F。

然后在自己排下，注意DE不能同时出现在第一排，其实也就是C42-1=6-1

yaoyao880529

1.根据题目可得有票的人中（1-60%)的人带车，又知道所有人中，有票带车的人占20%，那么有票的人在总人数的比例就是20%/40%啦

  这种题如果想不明白就画个图或者列个表就好了

2.题目是说有t的话，t+2肯定在集合中，如果集合第一个数字就是-1呢，那么其余所有的数只能比-1大

3.我觉得这题选A，第二个条件肯定不行

4.题目是说6个人排成两行，每排中右边的人都要比左边的高，后边的人要比他正对着的前排的人高，问这样的排列有几种，用枚举法就可以做

夕愫

设TOTAL的乘客为X，设round-trip的乘客为Y，因此我们要求的值就是Y/X

20%的TOTAL乘客又有票又有车

60%的有票的乘客没有车，意味着剩下40%有票的乘客又有车

可以得出等式   20%X=(1-60%)Y  就可以得到Y/X=50%

yjz809

同意3楼的，第三题第二个条件应该不正确

ryan123

其实第三题最简单的方法我认为还是画6条不同长度的先摆一下最安全，最快的

如果实战数学和GWD那么简单的话