Combination/Permutation

Question

Password codes consist of two letters (26 letters in the alphabet), followed by five digits (0-9). How many different password possibilities exist if repetition is allowed? How many different password possibilities exist if repetition is not allowed?

Answer 1

the passwords consist of L L D D D D D (L=letter and D=digit)

with repetition...

26*26*10*10*10*10*10=676*100,000=67,600,000 possibilities

without repetition...

26*25*10*9*8*7*6=650*30,240=19,656,000 possibilities