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Bunuel
A number that is a palindrome reads the same way forwards and backwards. For example, 3113 and 7447 are palindromes. Let n be the product of all 4-digit palindromes. What is the unit’s digit of n?

A. 0
B. 2
C. 4
D. 5
E. 8

We know that we will have at least one number that ends in a 5 and one number that ends in a 2. So we need something that is a multiple of both 5 and 2. All multiples of 5 and 2 are multiples of 10, and all multiples of 10 end in zero.

Answer choice A.
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Here we only care about the units digit.

We know that the palindromes can finish by any number between 1 and 9, equivalent to 9! if you are looking for the unit digit.

Any factorial after 5! will have trailing zeroes, so the product 9! will end with a 0
AnswerA
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