Re: [計量] 求救兩題GWD
※ 引述《oranger (從新出發)》之銘言：
: GWD3-18
: Last year the price per share of Stock X increased by k percent and the
: earnings per share of Stock X increased by m percent, where k is greater
: than m. By what percent did the ratio of price per share to earnings per
: share increase, in terms of k and m ?
: Ans: [100(k-m)]/(100+m)%
: GWD5-28
: 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
: Newapaper 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 ?
: Ans: 400p/(500-p)
: 請幫忙解答一下,謝謝!!
回答一下 GWD 5-28
設 newspaper A 賣 A分 newspaper B 賣 B分
方程式1. (A+1.25B)r=A ==> A=1.25Br/(1-r) 代入方程式2
方程式2 (A+B)p= B
==> 1.25pBr/(1-r) + BP = 1.25Br/(1-r)
==> 消B & 通乘 (1-r)
==> 1.25pr + p-pr= 1.25r
==> 移項 r(1.25-1.25p+p)=p
==> r= p/ (1.25-0.25p)
這邊我也有問題 通乘 400後得 r=400p/(500-100p) 不過我還是挑了這個答案 因為
沒得選 orz 拜託大家看看哪邊有錯囉
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