对两道题的答案有质疑

Q14:

$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

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

Answer: D

个人觉得条件一的表述似乎是说某个t时刻的量，并没有说是3。大家觉得呢？

Q17:

In the figure, points A, B, C, D, and E lie on a line.  A is on both circles, B is the center of the smaller circle, C is the center of the larger circle, D is on the smaller circle, and E is on the larger circle.  What is the area of the region inside the larger circle and outside the smaller circle?

(1)     AB = 3 and BC =2

(2)     CD =1 and DE = 4

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

Answer: A

我觉得应该选D，条件二可以推出小圆半径

呵呵，第一题，确实t没有说是3，但是t大于等于1吧，你代入试试，什么情况下{1+(r/100)}^t是1.1呢？所以不用知道t是多少。

对第二题我有印象，是一个内切的两个园，答案是错了，应该是D。

jetking，你的意思是说因为只有r=10时，t=1是上述表达式的唯一整数解，所以可以知道r的值，是这样吗？

这道题挺有意思，多谢！

第二题根据(2)推出的答案不唯一

小圆的半径可能为1或3

因此选A