[Q. ] A2GMAT KH數學GWD難題解析

[SHAOCHU (月台上的觀察員)]

This year Henry will save a certain amount of his income, and he will spend
the rest.  Next year Henry will have no income, but for each dollar that he
saves this year, he will have 1 + r dollars available to spend.  In terms of
r, what fraction of his income should Henry save this year so that next year
the amount he was available to spend will be equal to half the amount that he
spends this year？
(A)1/(r+2)   (B)1/(2r+2)   (C)1/(3r+2)   (D)1/(r+3)   (E)1/(2r+3)

[解]假設今年收入為i元，而今年存下s元，

亦即今年花費為i-s元，明年可花費s(r+1)元。題幹要求s/i的值。

依據題意，明年花費是今年花費的一半，可以列式：

s(r+1)=(1/2)(i-s)，得到s=[1/(2r+3)]i，所以s/i=1/(2r+3)，

選E。

--
各位朋友們大家好, KH目前為A2GMAT首席顧問,負責協助同學考取高分！
也於實戰上考取51分滿分多次, 本身數學教學經驗超過八年,目前也可家教 
數學機經班破700分同學為業界第一！有需要請直接來信: [e-mail]

A2GMAT KH數學機經班  http://a2gmat.blogspot.tw/p/blog-page.html
A2GMAT KH數學精修班  http://a2gmat.blogspot.tw/p/blog-page_23.html

--
※ 發信站: 批踢踢實業坊(ptt.cc), 來自: 180.177.216.107
※ 文章網址: http://www.ptt.cc/bbs/GMAT/M.1414428301.A.5E3.html