GWD 6-28

[jay41]

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 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)

可是我化簡到最候會變成p/1.25-0.25p
再同乘4變成4p/5-p
若要符合答案選項中的模式，
就再同乘100變成400p/500-100p
和答案的400p/500-p不同

哪裡有錯呢？

[8妹]

http://www.formosamba.com/phpBB3/viewtopic.php?t=2358

[micht]

trish8m~~屑屑~~

math版題目一堆 ..一題一post 我整理題目要花多少時間ㄚ........ :'(
大家這樣一個問題一篇另我很頭痛@@

[8妹]

不客氣啦~~ i82

[blue123736]

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 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)

可是我化簡到最候會變成p/1.25-0.25p
再同乘4變成4p/5-p
若要符合答案選項中的模式，
就再同乘100變成400p/500-100p
和答案的400p/500-p不同

哪裡有錯呢？

這題我上次做的時候也求出跟你一樣的東西
我記得問題好像主要是出在r percent 跟p percent
看在計算的過程中定義r 或p等於？
按字面上的意思r與p應該各是一個介於0到100之間的整數 （ex. r percent=32 percent=32% => r=32!!）
但也可視為各等於一個介於 0到1之間的小數（ex.r percent = R=32% => R=0.32）

用哪一種的定義都可以算出正確答案
但是記得分子分母上下的定義需一致

好像是這樣吧... :P

[micht]

不好意思 奇怪 這題numbering有問題 不是gwd8-25 !!!

[blue123736]

不好意思 奇怪 這題numbering有問題 不是gwd8-25 !!!

說的也是ㄟ....

翻了一翻 應該是GWD6-28 ;)

[micht]

感謝 blue123736 :D

馬上更正

[jay41]

一時打太快，手誤啦.............
歹勢ㄋㄟ................. :P

[chris8888]

各位同協,

1. 假設銷售量(A報和B報合計) = a份

2. A報收益 : a * p * $1.00
B報收益 : a * (1-p) * $1.25

3. ap / (ap + 1.25a(1-p)) => 化簡 => p / (1.25 - 0.25p) => 上下同乘以400 => 400p / (500 - p)

[livory]

我還是不太懂 P%/[P%+(1-P%)1.25]=R% 這段?
為什麼 P%要去除以後面那段式子?
題目中有說嗎?
煩請大牛們解答! 謝謝!