Madam, I'm Adam
A number is called a palindrome if it reads the same forwards and backwards. How many 5-digit palindromes are there?
Details and assumptions
12321 is a palindrome, while 12345 is not a palindrome.
The number is a 2-digit number, not a 3-digit number.
The answer is 900.
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1 solution
There are 9 choices for what the first digit of the palindrome could be, since the first digit cannot be zero. The last digit will be the same as this. There are 1 0 choices for what the second digit could be, and the fourth digit will be the same as this. There are also 1 0 choices for that the middle digit could be. Since we are choosing a first, second, AND third digit, we use the rule of product. In total there are 9 × 1 0 × 1 0 = 9 0 0 5-digit palindromes.