2. 外语
  3. A box contains 5 orange disks, 4 red disks, and 1 blue disk. You are to select two disks at random and without replacement from

A box contains 5 orange disks, 4 red disks, and 1 blue disk. You are to select two disks at random and without replacement from

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问题 A box contains 5 orange disks, 4 red disks, and 1 blue disk. You are to select two disks at random and without replacement from the box. What is the probability that the first disk you select will be red and the second disk you select will be orange?
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答案2/9
解析 To solve, you need to calculate the following two probabilities and then multiply them.
    The probability that the first disk selected from the box will be red
    The probability that the second disk selected from the box will be orange, given that the first disk selected from the box is red
The probability that the first disk you select will be red is. If the first disk you select is red, there will be 5 orange disks, 3 red disks, and 1 blue disk left in the box, for a total of 9 disks. Therefore, the probability that the second disk you select will be orange, given that the first disk you selected is red, is. Multiply the two probabilities to get .
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