Mock AIME 5 2005-2006 Problems/Problem 13

Problem

Let $S$ be the set of positive integers with only odd digits satisfying the following condition: any $x \in S$ with $n$ digits must be divisible by $5^n$. Let $A$ be the sum of the $20$ smallest elements of $S$. Find the remainder upon dividing $A$ by $1000$.

Solution

Solution

See also

Mock AIME 5 2005-2006 (Problems, Source)
Preceded by
Problem 12
Followed by
Problem 14
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