请教Prep PS1-62。题意不明。

bipedalism

62.   7564-!-item-!-187;#058&005577

Alice's take-home pay last year was the same each month, and she saved the same fraction of her take-home pay each month.  The total amount of money that she had saved at the end of the year was 3 times the amount of that portion of her monthly take-home pay that she did not save.  If all the money that she saved last year was from her take-home pay, what fraction of her take-home pay did she save each month?

 

(A) 1/2

(B) 1/3

(C) 1/4

(D) 1/5

(E)  1/6

请教题意。谢谢NN指教。

crazecat123

s = monthly saved, ns = monthly not saved

s * 12 = ns * 3
s / ns = 3 / 12 = 1 / 4

=> s / (s + ns) = 1 / 5

bipedalism

不对啊。ns这块，也是12个月的啊。怎么会只ns*3呢？请指教

mymengming

同意2楼的

这题关键是对The total amount of money that she had saved at the end of the year was 3 times the amount of that portion of her monthly take-home pay that she did not save.  的理解

The total amount of money （that she had saved at the end of the year） was 3 times the amount
            of that portion of her monthly take-home pay （that she did not save）. 

sausau

我错了

lxw19

这道题应该如何求解呢？请教nn

lxw19

顶顶

jqf2416

设每月take-home pay 为x，每月存入银行的比例为y
12xy=3x（1-y），化简后y=1/5

lxw19

12y 代表是 the total amount of money that she had saved at the end of the year， 请问为什么要乘以 x呢

jqf2416

12y 代表是 the total amount of money that she had saved at the end of the year， 请问为什么要乘以 x呢

-- by 会员 lxw19 (2010/3/16 14:43:58)

不好意思 我表达的有歧义， y代表存入银行的钱和总钱数的比例， y是个比例