小女子跪求！GWD弟5套的28题求解求解很郁闷解不出

FANLIZHOU1 · 发表于 2011-5-22 23:05:10

Q28:

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)

在试卷里这个题就被标记为红色字体小女子实在解不太明白请高手指点！谢谢！

FANLIZHOU1 · 发表于 2011-5-22 23:09:18

请高手指点！！！跪求！！

FANLIZHOU1 · 发表于 2011-5-22 23:13:14

请高手指点！！！跪求！！

-- by 会员 FANLIZHOU1 (2011/5/22 23:09:18)

我也不知道这个题在试卷里为什么就已经是红色了怎么解都解不出答案里的式子。。

Avengeryzc · 发表于 2011-5-23 02:17:43

Let the total newspaper sold be 100.

Newspaper A sold = p
Newspaper B sold = 100-p
Total revenue = p*1+(100-p)*1.25
So revenue from paper A = p*1 = p
Revenue percentage from paper A = (p/(p+(100-p)*1.25))*100
This is equal to r
thus
(p/(p+(100-p)*1.25))*100 = r

=> r = 100p/(125-0.25p)
r = 400p/(500-p)

Hence the answer.

FANLIZHOU1 · 发表于 2011-5-23 08:15:28

Let the total newspaper sold be 100.

Newspaper A sold = p
Newspaper B sold = 100-p
Total revenue = p*1+(100-p)*1.25
So revenue from paper A = p*1 = p
Revenue percentage from paper A = (p/(p+(100-p)*1.25))*100
This is equal to r
thus
(p/(p+(100-p)*1.25))*100 = r

=> r = 100p/(125-0.25p)
r = 400p/(500-p)

Hence the answer.

-- by 会员 Avengeryzc (2011/5/23 2:17:43)

eh.. but here said" if p percent of the newspapers that the store sold were copies of newspaper B, " not A, So,,, I think something wrong with it,,

I have no idea for this question... Dm..

小女子跪求！GWD弟5套的28题求解求解很郁闷解不出

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