Given N integers a₁, a₂, ... a_N prove there exists a (non empty) subset whose sum is a multiple of N. (Allow repeated numbers in both the original set and its subsets.)

Look at perplexus.info/show.php?pid=632 for a particular case of this problem -- and a totally different solution.

Posted by Old Original Oskar! on 2005-09-01 16:24:59