To find the Least Common Multiple you first have to write down multiples of each number until one same multiple occurs in both lists. Once you find that multiple you can circle it to use it in your answer.
To find the greatest common factor you just have you list all the factors of that number and the other's too. Then you circle the largest factor that occurs in both lists.
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.
