- #1

dancergirlie

- 200

- 0

## Homework Statement

Prove that every positive integer is congruent to the sum of its digits (mod 9). (for example 38 is congruent to 11(mod 9))

## Homework Equations

If a is congruent to b (mod n), then n divides (a-b)

## The Attempt at a Solution

let a= {a1, a2... a9} be digits

where 0 is less than or equal to a which is less than 10

That is where i don't know where to go, i have these digits and I don't know how to show that when added together they = b(mod 9)

maybe i should do something about 9 divides some digits, but i have no clue.

Any suggestions or tips would be great =)