One thing to remember is that a number is divisible by 3 if the sum of all its digits is divisible by 3.Since 0 is not allowed and removing any one of the 4 digits results in a number divisible by 3, there're types of possibilities:1. all 4 digits are the same, there're 9 possibilities: 1111, 2222, ..., 99992. all digits a...
