再问一题prep数学-59

ann110726 · 发表于 2010-1-28 15:34:57

59. 4950-!-item-!-187;#058&004329
Ann deposited money into two new accounts, A and B. Account A earns 5 percent simple annual interest and account B earns 8 percent simple annual interest. If there were no other transactions in the two accounts, then the amount of interest that account B earned in the first year was how many dollars greater than the amount of interest that account A earned in the first year?

(1) Ann deposited $200 more in account B than in account A.
(2) The total amount of interest that the two accounts earned in the first year was $120.

此题如何做呢？

貌似条件2就可以啦
120=1.08x+1.05y，不能凑出来呢？

kazuyafq · 发表于 2010-1-28 15:58:44

条件1,假设ANN在A里面存了X,那么A帐户第一年利息就是0.05X,B就是0.08(X+200)=0.08X+16,(0.08X+16)/0.05X,由于X无法确定,所以无法独立算
条件2,120=0.05X+0.08Y,X和Y的解是不唯一的.
条件1+条件2,那么就是120=0.05X+0.08(X+200)=0.13X+16,X=800,Y=1000,利息就是A 40,B 80,所以就是2倍

个人意见哦~~

ann110726 · 发表于 2010-1-28 16:06:39

感谢！

再问一题prep数学-59

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