(See attached file for full problem description)
Let d,m and n be positive integers with m>1 and m≡ 1 (mod d), let
be the base=m expansion of n, and let
f = c0+c1+c2+c3+...+cr
Prove that n is divisible by d if and only if f is divisible by d.
This is a discrete math proof of divisibility.