Answer (13 of the original arrangements are duplicates now, as
AAAF F F FDDDDCC, AAF F F FDDDDCCA, ..., CAAAF F F FDDDDC
are identical): 900900/13 = 69300.
Every number that has 0 as last digit and isn't decimal number, can be divided by 10 without remainder. It works for both positive or negative numbers. If last digit is different from 0, you will have remainder equal to that last digit. Even number 0 is divisible by 10 (the answer is 0 of course) because its last and only digit is 0.
