If $1,000 will be deposited in a bank account and I is the dollar amount of interest earned from the original deposit, represented as I = 1000 {(1 + r/100)n – 1}, and the annual interest rate is r percent, is r > 8 percent?
(1) The deposit earns a total of $210 in interest in the first 2 years.
(2) (1 + r/100)2 > 1.15
我觉得应该是A,但是答案给出是D,请大家讨论,谢谢!
我是这么想的饿。
条件(1)1000{(1+r/100)^2-1)}=210得出(1+r/100)^2=1.21
算出r/100=0.1,r=10% 可以得出r>8%
条件(2)把r=8%代入第二个条件,得出1.08^2<1.15,而条件中给出的
(1+r%)^2>1.15>(1+8%)^2
所以也可以得出r>8%.
所以选D.
不知道这样说有没有弄清楚?
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