鲁教版七年级数学配套练习册习题7.5第五题答案

设1000元年利率为x,20000元年利率为（0.0297-x）.
1000x+20000(0.0297-x)=457.2
1000x+594-20000x=457.2
-18000x=457.2-594
-18000x=-136.8
18000x=136.8
x=0.0076
0.0297-x=0.0297-0.0076=0.0221
0.0076=0.76% 0.0221=2.21%
答：1000元年利率为0.76%,20000元年利率为2.21%.