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GMAT GoGo
Jul 30, 2007, 4:26:42 AM7/30/07
to GMAT 700+
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?
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)
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Rohto
Jul 30, 2007, 7:48:58 AM7/30/07
to GMAT 700+
初中数学知识，温故拉...
题目意思是星期天某商店只卖了两份报纸A & B, A单价$1.00, B单价$1.25, 其中报纸A买的所挣收入占总收入的r%, A卖掉的份
数
占卖掉总份数的p%, 问r与p之间的关系表达
解：思路：列方程组，消未知数，
已知条件：For newspaper A-- price $1.00, Revenue(%) r, copies(%) p; B
price $1.25, Revenue(%) 1-r, copies(%) 1-p
设报纸A卖了x份，B卖了y份，列方程组：
r /100= 1*x/ (1*x+1.25*y)
p/100= x/(x+y)
化简通过x/y消掉未知数 r=400p/(500-p) so key D is right
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