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标题: 求解一道题 [打印本页]

作者: greates 时间: 2010-3-22 07:22 标题: 求解一道题

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)

500p / (625 – p)
答案是D 求过程

作者: myice 时间: 2010-3-23 11:10

题目不对吧，应该是
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 A,which of the following expresses r in terms of p?
这样算出来是D呢~~~

作者: liuzhenlin 时间: 2010-3-23 21:06

总的revenue是 T=1*m+1.25*n, 其中m是A的份数，n是B的份数
由题可知 r/100 * T= 1*m----------1

p/100*T=1.25*n----------2
1+2得：r/100*T+p/100*T=T，消去T

所以r+p=100
所以D对。应该是这样

作者: aobailing 时间: 2010-3-24 07:02

p是份数百分比， p/100*T=1.25*n----------2 不成立

作者: norgar 时间: 2010-3-25 06:53

不对呀 r+p=100是前提。。。

俺也不懂。。同求助

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