MathNet 2016-part-04 — 184 problems (EN–VI) Question 103

Consider nine 9-digit numbers (not necessarily distinct), each contains exactly the digits $1, 2, 3, 4, 5, 6, 7, 8, 9$ (in some order). The sum of these nine numbers ends with $k$ zeroes. Determine the maximal possible value of $k$.