Problem

Source: 2000 Estonia National Olympiad Final Round grade 9 p2

Tags: number theory, Digits, Digit



In a three-digit positive integer $M$, the number of hundreds is less than the number of tenths and the number of tenths is less than the number of ones. The arithmetic mean of the integer three-digit numbers obtained by arranging the number $M$ and its numbers ends with the number $5$. Find all such three-digit numbers $M$.