AMC 8 2007 Problem 25

AMC8 2007 年第 25 题

概率★★★★☆
On the dart board shown in the figure, the outer circle has radius 6 and the inner circle has a radius of 3. Three radii divide each circle into three congruent regions, with point values shown. The probability that a dart will hit a given region is proportional to the area of the region. When two darts hit this board, the score is the sum of the point values in the regions. What is the probability that the score is odd?
在如下图所示的飞镖盘上，外圈的半径为 6，内圈的半径为 3。三个半径将每个圆分成三个全等区域，每个区域的分值如图所示。飞镖击中给定区域的概率与该区域的面积成正比。当两个飞镖击中此飞镖盘时，总分为所击中的各区域的分值之和。则总分为奇数的概率是多少？
  1. A.1736\displaystyle \frac{17}{36}
  2. B.3572\displaystyle \frac{35}{72}
  3. C.12\displaystyle \frac{1}{2}
  4. D.3772\displaystyle \frac{37}{72}
  5. E.1936\displaystyle \frac{19}{36}

正确答案 · Correct Answer

B

解析 · Solution

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