请教一道数学题~NN帮忙唷

ruiqijjkkl

If $1,000 is deposited in a certain bank account and remains in the account along with any accumulated interest, the dollar amount of interest, I , earned by the deposit in the first n years is given by the formula I =1000〔(1 +r/100)ⁿ - 1〕, where r percent is the annual interest rate paid by the bank.Is the annual interest rate paid by the bank greater than 8 percent?



(1)The deposit earns a total of $210 in interest in the first two years.

(2)( 1 + r/100)² > 1.15

--------------------------------------------------------------------------------------------------------------------------
【答案】A

请问：没有计算器岂不是要算很久。。。真实考试里面这样的题目多不多啊

ruiqijjkkl

我的意思是涉及到开平方的问题。。

海诺薇拉

不用开平方啊，1.08^2算下就可以啦，计算量不会很大嘛。。。

ruiqijjkkl

我还是觉得很容易搞错の，不等号一加就乱套了~~
想不清楚的时候就想大于1.08和小于1.08的数都带进去算算。。
或者举其他简单的例子，先把关系弄明白再说。。