March 9–March 15, 2010

Problem

Prove that for all natural numbers n, there exists an n digit number, divisible by 5n, all of whose digits are odd.

Solution

here

List of solvers

Lloyd Sakazaki, Pelyush Jain, Mike Goodman, Wenqian Wang, T.R. Mukundan, Enkhbileg Ganbat (outside).

Wenqian Wang wins the prize!