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GWD 答案的可信度有多高?

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楼主
发表于 2010-11-10 23:50:32 | 只看该作者 回帖奖励 |倒序浏览 |阅读模式
有哪位知道GWD答案的可信度有多高? 做完了一对,好多题跟答案都不一样,看了几遍也说服不了我,觉得我的答案是对的。呵呵。。。。。。

还有请大家帮帮忙解决一道题:
Last Sunday a certain store sold copies of Newspaper A for $1.00 each and copies of Newspaper B for $1.25 each, and the store sold no other newspapers that day.If r percent of the store’s revenues from newspaper sales was from Newspaper A and if p percent of the newspapers that the store sold were copies of newspaper B, which of the following expresses r in terms of p?



A.100p / (125 – p)

B.150p / (250 – p)

C.300p / (375 – p)

D.400p / (500 – p)

E.500p / (625 – p)
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沙发
 楼主| 发表于 2010-11-10 23:59:39 | 只看该作者
还有一题:


If the number 52,1n9, where n represents the tens digit, is a multiple of 3, then the value of n could be which of the following?

A.    6
B.    5
C.    3
D.    1
E.    0
板凳
发表于 2010-11-11 01:09:02 | 只看该作者
有哪位知道GWD答案的可信度有多高? 做完了一对,好多题跟答案都不一样,看了几遍也说服不了我,觉得我的答案是对的。呵呵。。。。。。

还有请大家帮帮忙解决一道题:
Last Sunday a certain store sold copies of Newspaper A for $1.00 each and copies of Newspaper B for $1.25 each, and the store sold no other newspapers that day.If r percent of the store’s revenues from newspaper sales was from Newspaper A and if p percent of the newspapers that the store sold were copies of newspaper B, which of the following expresses r in terms of p?



A.100p / (125 – p)

B.150p / (250 – p)

C.300p / (375 – p)

D.400p / (500 – p)

E.500p / (625 – p)
-- by 会员 chenzhencaiya (2010/11/10 23:50:32)



求解释
地板
发表于 2010-11-11 01:11:26 | 只看该作者
还有一题:


If the number 52,1n9, where n represents the tens digit, is a multiple of 3, then the value of n could be which of the following?

A.    6
B.    5
C.    3
D.    1
E.    0
-- by 会员 chenzhencaiya (2010/11/10 23:59:39)



if 521n9 mod 3 =0
then 5+2+1+n+9 mod 3 =0
17+n mod 3 =0, 0<=n<=9
n=1 or 4 or 7
5#
发表于 2010-11-11 01:57:29 | 只看该作者
个人认为:最后一个B改成A就可以算出d答案
6#
发表于 2010-11-11 05:27:59 | 只看该作者
两个都选d吧
7#
发表于 2010-11-11 05:42:32 | 只看该作者
还有一题:


If the number 52,1n9, where n represents the tens digit, is a multiple of 3, then the value of n could be which of the following?

A.    6
B.    5
C.    3
D.    1
E.    0
-- by 会员 chenzhencaiya (2010/11/10 23:59:39)




if 521n9 mod 3 =0
then 5+2+1+n+9 mod 3 =0
17+n mod 3 =0, 0<=n<=9
n=1 or 4 or 7
-- by 会员 cateatingfish (2010/11/11 1:11:26)



请教:是不是只有3的倍数 才有这个性质阿,2的倍数,5的倍数都不行好像。还有其他数字有这个规律吗?多谢指教
8#
发表于 2010-11-11 06:53:09 | 只看该作者
Only 3的倍数 has this property. I thought most Chinese student learned this in middle school.

For 2的倍数 : Always end with a digit of 0, 2, 4, 6 or 8.

For 5: Always end with a digit of 0 or 5

For 6: combination of requirements for 2 and 3
9#
 楼主| 发表于 2010-11-11 11:08:24 | 只看该作者
Thanks for the explanation! short and sweet, easy to understand!
10#
发表于 2010-11-11 11:41:52 | 只看该作者
Last Sunday a certain store sold copies of Newspaper A for $1.00 each and copies of Newspaper B for $1.25 each, and the store sold no other newspapers that day.If r percent of the store’s revenues from newspaper sales was from Newspaper A and if p percent of the newspapers that the store sold were copies of newspaper BA, which of the following expresses r in terms of p?



A.100p / (125 – p)

B.150p / (250 – p)

C.300p / (375 – p)

D.400p / (500 – p)

E.500p / (625 – p)

LZ, you made a mistake in your original problem.  Both r and p are percentages related to newspaper A.


categories A newspaper  B newspaper
price               1                    1.25
sold copies      x                       y
revenue          x                    1.25y

p = (100*x)/(x + Y)  --> y = (100 - p)*x/p

r= (100 * x)/(x + 1.25Y) = (100 * x)/[x + 1.25 * (100-p) * x/p] = 100/[1 + (500 - 5p)/4p] = 400p/(500-p)

Answer D
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