Of the two-digit positive integers less than 20 how many have different digits

分类: 作业答案 • 2021-12-31 22:34:40

问题描述：

Of the two-digit positive integers less than 20 how many have different digits
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答

小于20的两位数的正整数中,个位和十位上的数字不同的数字有几个?