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标题: 这道GWD该怎么做呢？没有思路呀！！ [打印本页]

作者: hebeqiao 时间: 2007-12-30 05:40
标题: 这道GWD该怎么做呢？没有思路呀！！

If n is a positive integer and r is the remainder when (n-1)(n+1) is divided by 24, what is the value of r?

(1)
2 is not a factor of n.

(2)
3 is not a factor of n.

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.

Answer: c

作者: hebeqiao 时间: 2007-12-30 05:42

Q14: is the answer wrong?

How many seconds will it take for a car that is traveling at a constant rate of 45 miles per hour to travel a distance of 22 yards? (1 mile = 1,160 yards)

A. 8

B. 9

C. 10

D. 11

E. 12

Answer: c

作者: yankevi 时间: 2007-12-30 06:09

楼主那个n-1和n+1的是不是选C?r=0

作者: hebeqiao 时间: 2007-12-30 07:59

是呀，为什么呢？

作者: yankevi 时间: 2007-12-30 08:27

不好意思，才看到你的回帖，是这样的，根据1的话，说明n是奇数，设n=2a+1.

那么n-1*n+1=4*a*(a+1)这个数是能被8整数的（a*a+1因为连续的整数相乘被2整数）。。但是和24不知道了。。

根据2.。不能被3整数，设n=3b+1或者3b+2

那么n-1*n+1=3b(3b+2)说这个这个数能被3整数

那么这个数又能被3整数，又能被8整数，肯定能被24整数。。所以余数为0

作者: hebeqiao 时间: 2007-12-30 10:00
Thanks a lot!!

作者: hebeqiao 时间: 2007-12-30 10:07

祝成功杀鸡！

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