GWD1-19

[la-vie]

Q19:
A total of $60,000 was invested for one year. But of this amount earned simple annual interest at the rate of x percent per year, and the rest earned simple annual interest at the rate of y percent per year. If the total interest earned by the $60,000 for that year was $4,080, what is the value of x?
(1) x = (3/4) y
(2) The ratio of the amount that earned interest at the rate of x percent per year to the amount that earned interest at the rate of y percent per year was 3 to 2.


答案是C

[cutefox0108]

我也不會耶~~頂一下
我將2個條件何起來後得出

1...p*x+(60,000-P)y=4080
2...p*x/[(60,000-P)*y]=3/2
整理後
(60,000-P)*y=1632

還是有兩個未知數耶~~解不出X

[quentas]

p*x/[(60,000-P)*y]=3/2

展開後搭配x=3/4 y可以消去y

p即可得 則x y可得

[smilego]

1) A*3Y/4+(60000-A)Y=4080
2) 2AX =3*(60000-A)Y

這題算式我一直解不出來,請問有人可以幫忙列出整個算式嗎?? 謝謝

[christinehsu]

不好意思 ，我有點看不懂你的A是什麼。
我用我的算法給你看一下。

設投資在X%年利率的錢為W，那麼投資在Y%年利率的金額就為(60000-W)
在著，由第一個條件可以得知Y=3/4X
所以可以得知下面的式子
(WX)+{(60000-W)*3/4X}=4080

所以由第二個條件可以得知WX=3/5(4080)=2448
=>=>=> (60000-W)*3/4X=1632
之後就可以解出X等於多少