gwd30-Q10

[dianechiu]

$10,000 is deposited in a certain account that pays r percent annual interest compounded annually, the amount D(t), in dollars, that the deposit will grow to in t years is given by D(t)=10,000{1+(r/100)}^t. What amount will the deposit grow to in 3 years?

(1) D(t)=11,000
(2) r=10

Ans:(D)

(1) D(t)=10,000{1+(r/100)}^t=11,000=>三年後存款即是11,000元=>充分
(其實加上(1)的條件,不論幾年後存款都會是11,000元)

(2)r=10,t=3,代入D(t),即可求解=>充分

兩條件均單獨充分,故答案是(D)

不知道這樣的思路對不對? 謝謝

之前寫的時候選(B),因為覺得D(t)=11,000=10,000{1+(r/100)}^t, t和r均未知,無法求解不充分 (完全忘記題目設定t=3...)

[dibert8]

同意這樣的理解.