趣味的數學-46
正整數集 {1000, 1001, 1002,...,2000} 中有多少對連續的整數在相加時不需要進位?
【原文】 For how many pairs of consecutive integers in the set {1000, 1001, 1002, ..., 2000} is no carrying required when the two integers are added?
【轉引自Titu Andreescu等編著的102 Combinatorial Problems 第15題】
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