单选题
【正确答案】
C
【答案解析】Let r and R be the radii of the two circles. From the figure, you can see that ΔOAB is a 45-45-90 right triangle, and so R = [*] (KEY FACT J8). Therefore,
[*]
[*][*] The ratio is 2:1.
**Do exactly the same thing except use TACTIC 2, Chapter 11. Let r = 1 ; then R = [*]and the ratio is [*]
[*]
[*][*] The ratio is 2:1.
**Do exactly the same thing except use TACTIC 2, Chapter 11. Let r = 1 ; then R = [*]and the ratio is [*]
【正确答案】
D
【答案解析】If x = 3 and y = 7 (or vice versa), then x + y = 10, and Column B is greater. Eliminate Choices A and C. If x = 1 and y = 21 (or vice versa), then x + y = 22. This time, Column A is greater. Eliminate Choice B. Neither column is always greater, and the two columns are not always equal.