2009 AMC 8 第 13 题
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13.
一个三位整数包含数字 、、 各一次。这个整数能被 整除的概率是多少?
A three-digit integer contains one of each of the digits and What is the probability that the integer is divisible by
小提示:
一个数能被 整除,当且仅当末位数字是 或
A number is divisible by exactly when its last digit is or
大提示:
对数字 、、,每个数字作为末位的可能性相同
With digits and each digit is equally likely to be last.
解答:
这个数以 、 或 结尾的可能性相同。
只有当末位是 时,它才能被 整除,概率为 。
所以正确答案是 B。
The number is equally likely to end in or
It is divisible by only if the last digit is which happens with probability
Thus, B is the correct answer.
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