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Challenge 80 Answer


5-digit palindromes

For the first digit we have 9 options (cannot start with zero).

For the second and third digits we can accept any number between 0 and 9 (ie we have 10 options).

For the fourth and fifth digits, there is only one option, as they must be equal to the second and first digits, respectively.

ABCBA = 9 x 10 x 10 x 1 x 1 = 900

There are 900 5-digit palindrome numbers!

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