请教一道关于投资的题

promiselu

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.
    
A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.

and the rest earned simple annual interest at the rate of y percent per year，这个the rest指的是第一笔钱赚的利息吗？ 可是只投资了一年，而且是每年计一次的单利，利息怎么会在第一年就赚钱呢？

fangpyj8906

这道题讲的是说总共有60000的资金投资一年，一部分按Xpercent 的年利率单利计息，剩下的部分按Ypercent 单利计息，又说这年投资总的利息额是4080，求利率X。
设按X利率投资的部分为A，按Y利率投资的部分为B则列出方程 A+B=60000，AX+BY=4080，根据条件一得出X和Y的关系，题目要求X，但是有四个未知数三个方程没所以不充分；条件二：AX：BY=3:2，也是只有三个方程，求不出来，所以1+2就能得到四个方程四个未知数，就能求出X了

promiselu

正解！ 谢过~