最新提问
我的动态
登录后查看动态
题目内容双击单词支持查询和收藏哦～
A certain personal identification number (PIN) for opening garage doors is a sequence of $$4$$ digits, where each digit is selected from the digits $$0$$ to $$9$$. How many such PINs have at least two different digits and are palindromes?
(Note: A palindrome is a sequence of characters that reads the same backward and forward. For example, $$1,221$$ is a palindrome.)
(Note: A palindrome is a sequence of characters that reads the same backward and forward. For example, $$1,221$$ is a palindrome.)
B显示答案
· 相关考点
6.3.2 乘法原理 7.3.3 加试转算分题
6.3.2 乘法原理
7.3.3 加试转算分题
以上解析由 考满分老师提供。
