【正确答案】 C

【答案解析】In each triangle the largest angle is the sum of the two smaller ones (3 = 1 + 2 and 9 = 2 + 7), so each is a 90°angle. The columns are equal (C).
**Use TACTIC D2: In ratio problems, write x after each number and solve.
Column A: x + 2x + 3x = 180 [*] 6x = 180 x = 30 [*] 3x= 90.
Column B: 2x + 7x + 9x = 180 [*] 18x= 180[*]x =10[*]9x=90.

【正确答案】 B

【答案解析】The perimeter of the shaded region is given as 4 + 2re. You can easily prove that the lengths of the curved parts of the region are 2π and that the straight edges have a total length of 4, but you should just assume these values. Then each side of the square is 2, and its area is 4. From that subtract π, the area of a circle (two semicircles) of radius 1.
[*]
Since π is slightly greater than 3, then 4 -π is less than 1. Column B is greater.