一题求比例的！

Xiaotongdi · 发表于 2011-4-17 16:06:49

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?

A.100p / (125 – p)
B.150p / (250 – p)
C.300p / (375 – p)
D.400p / (500 – p)
E.500p / (625 – p)
这类题怎么做呢？答案是D！

huxleyxu · 发表于 2011-4-17 16:35:02

另总的revenues为R，卖出的总数量为Q
根据题意有如下两个关系式

式一 (r%*R)/1.00=p%*Q
式二 [（1-r%)*R]/1.25=(1-p%)*Q

由一式得R=Qp/r-------式3
把式3带入式二整理得 r=400p/(500-p)

huxleyxu · 发表于 2011-4-17 16:37:20

还有别忘了r%=0.01r p%=0.01p

Xiaotongdi · 发表于 2011-4-17 16:47:49

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。原来是这么个意思！看来我是没明白意思！

huxleyxu · 发表于 2011-4-17 16:52:41

你的所有问题我都回答完了

Xiaotongdi · 发表于 2011-4-17 17:40:17

真的非常感谢啊！果真是NN！

一题求比例的！

所属分类: GMAT考试

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