2015 AMC 8 第 7 题
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所有题目均经美国数学协会（MAA）官方合法授权使用。
7.
两个盒子中各有三枚编号为 、、 的筹码。从每个盒子中随机取出一枚筹码，并将两枚筹码上的数字相乘。乘积为偶数的概率是多少？
Each of two boxes contains three chips numbered A chip is drawn randomly from each box and the numbers on the two chips are multiplied. What is the probability that their product is even?
小提示：
统计补集，也就是乘积为奇数，可能更容易
It may be easier to count the complement: an odd product.
大提示：
只有当两枚筹码都是奇数时，乘积才是奇数
The product is odd only if both drawn chips are odd.
视频讲解：
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文字解答：
只有当两枚筹码都是奇数时，乘积才是奇数。每个盒子中有两个奇数筹码 和 ，共三个筹码，所以乘积为奇数的概率是 。
乘积为偶数的概率是补集，等于 。
所以正确答案是 E。
The product is odd only when both chips are odd. Each box has two odd chips, and out of three chips, so the probability of an odd product is
The probability of an even product is the complement,
Thus, E is the correct answer.
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