Question

Find all 3-digit palindromes which are divisible by 11.
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Answer 1

Answer:

A 3 digit palindrome must be of the form aba, where a≠0 and b are digits. This divisible by 11 if and only if a-b+a = 2a-b is divisible by 11. This is possible only if 2a-b = 0, 11 or -11.