Pick 4 different numerals from 0 - 9 and arrange them to make the largest possible number.
|for example: 8732|
Now arrange the same numerals to make the smallest possible number.
Subtract the smaller number from the larger.
Arrange the numerals in the answer to make the largest and smallest possible numbers, and subtract those numbers.
Continue with this process until you end up with 6174.
Does it always work? Try 4 new numerals and see if you can end at 6174 every time!