三道怎么也想不通的题目,请教NN

hippocrene

谢谢这位N哥哥

hippocrene

这个意思啊，哭~~~~~~~`

specters

第三题

P(10,5)/P(10,4)

[此贴子已经被作者于2006-10-15 22:32:22编辑过]

specters

第二题看这个帖子

http://forum.chasedream.com/dispbbs.asp?boardID=22&ID=199841&page=1

specters

第一题n(n+1)(n+2)有两种情况可以被8整除

1. n为偶数，则n(n+2)必然可以被8整除；有48种可能

2. n为奇数，n(n+2)为奇数，要被8整除则(n+1)必须要是8的倍数；有12种可能

hippocrene

If an integer n is to be chosen at random from the integers 1 to 96, inclusive, what is the probability that n(n + 1)(n + 2) will be divisible by 8?

A)1/4

B)3/8

C)1/2

D)5/8

E)3/4

The number of defects in the first five cars to come through a new production line are 9, 7, 10, 4, and 6, respectively.  If the sixth car through the production line has either 3, 7, or 12 defects, for which of theses values does the mean number of defects per car for the first six cars equal the median?

I   3

II   7

III   12

A) I only

B) II only

C) III only

D) I , III only

E) I,II and III

If a code word is defined to be a sequence of different letters chosen from the 10 letters A, B, C, D, E, F, G, H, I, and J, what is the ratio of the number of 5-letter code words to the number of 4-letter code words?

A) 5 to 1

B) 3 to 2

C) 2 to 1

D) 5 to 1

E) 6 to 1

题目来自GWD，答案不重要，希望可以告知过程，第二题题意不太了解，希望NN帮我解释下，谢谢