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.)

(In reply to what is a subset? by Sir Percivale)

Right, the whole set is a subset of itself, though not a "proper" subset. The empty set is also a subset of any set, but isn't allowed here.

Posted by Old Original Oskar! on 2005-08-24 19:09:05