3道GWD的数学...请nn帮忙...

生活就是越狱

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

答案是D，但是我认为是E，因为如果－1在这个set中，那么相当于一个等差数列，.....－3、－1、1、3、5、7.....

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

不知该如何列式.........

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.

                  

本人认为选 C，答案是D。单独的（1）或（2）会解出两个答案。

请nn们帮忙，谢谢^_^

 

生活就是越狱

先自己顶一下！

排版不好，字体太小，请多多保函...

xma48215

先说第一题,因为题目给出的条件是t + 2 ,也就是说-1+2与1+2与3+2.....在此集合之中~这个集合也就是一个首项为-1公差为2的无穷等差数列~

NO.2:~你用用穷举法、I。125 346 II。124 356 III。123 456 IV。134 256 VI。135 246

前三个数代表第一排，后三个数代表第二排。

NO.3 你自己算一下,1和二两个都是只有一种情况的

[此贴子已经被作者于2008-5-6 15:32:10编辑过]

生活就是越狱

噢～非常感谢xma48215!!!