Numbers "ending" in the product of their digits
Source: Central American Olympiad 2007, Problem 5
June 12, 2007
Problem Statement
Given two non-negative integers , let's say that ends in if we can get by erasing some digits (from left to right) in the decimal representation of . For example, 329 ends in 29, and also in 9.
Determine how many three-digit numbers end in the product of their digits.