GWD 1- 25 & 27

leo_victor

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

正确答案是A, 但是我太确定，这道题应该怎么去想去思考。

我知道第一排的第一个， 和最后一排的最后一个， 是没得选的，分别是最矮和最高的那个人，但是其他四个人应该怎么安排，我就不太确定了，希望得到指点，谢谢。

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Q27:

If n = 8¹¹ – 8, what is the units digit of n?

 

A.     0

B.      1

C.      4

D.     6

E.      8

这题正确答案是C, 但是我就不知道该怎么个算法，肯定不会是那种傻算了。