2010 AIME II Problems/Problem 1

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Problem

Let $N$ be the greatest integer multiple of 36 all of whose digits are even and no two of whose digits are the same. Find the remainder when $N$ is divided by $1000$.

Solution

If assume to include all the even digits for the greatest integer multiple, we find that it is impossible for it to be divided by $3$ or $36$. The next logical try would be $8640$, and this happens to be divisible by $36$. Thus $N = 8640 mod 1000 = \fbox{640}$