1992 OIM Problems/Problem 1
Problem
For each positive integer , let
be the last digit of the number.
. Calculate
.
~translated into English by Tomas Diaz. ~orders@tomasdiaz.com
Solution
Let and
be integers with
, and
Since , then
Let
Alternate solutions are always welcome. If you have a different, elegant solution to this problem, please add it to this page.