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题目内容
A computer identification code on a certain machine consists of 2 letters from an alphabet of 26 letters, followed by 2 digits from the digits 0 to 9. The two digits must be different. How many identification codes are possible?
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· 相关考点
6.3.1 计数原理
6.3.1 计数原理
以上解析由 考满分老师提供。