SAT数学Problem Solving练习题（1）

>>SAT考试：SAT数学Problem Solving练习题（1）

>>SAT考试辅导：精品课程高端指导

Question #1: If a · b = 18 and a / b = 2, a > 0, b > 0 then:

(a) a = 18 and b = 1

(b) a = 9 and b = 2

(c) a = 18 and b = 9

(d) a = 6 and b = 3

(e) a = 6 and b = 6

Answer: a / b = 2

a = 2·b.

a·b = (2· b)· b

a·b = 2· b 2.

2· b 2 = 18

b 2 = 9,

b = 3 because b > 0,

a = 2· b

a = 6.

Question #2: The ratio of the radii of two circles is r1/r2 = 6. What is the ratio of the perimeters P1/P2 and the ratio of the areas of the two circles A1/A2?

(a) perimeter ratio = 1/6, area ratio = 36

(b) perimeter ratio = 36, area ratio = 6

(c) perimeter ratio = 6, area ratio = 36

(d) perimeter ratio = 1/8, area ratio = 8

(e) perimeter ratio = 1/6, area ratio = 6

Answer: r1 / r2 = 6;

Perimeter1 / Perimeter2 = (2· ¶· r1)/(2· ¶· r2) = r1/ r2 = 6

Area1 / Area2 = (¶· r12)/ (¶· r22) = r12 / r22 = 36

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