Question

5 identical country CDs and four identical rap CDs are to be placed in a display window. In how many ways can they be arranged? (permutations)
would anyone help me (not necessarily tell me the answer but give me hints)

Answer 1

P(n, r)
n = 9 because there are 9 CD's so there are 9 places to put them.
r = ?

Answer 2

since the counrty cd's are identical and the rap cd's are identical, we really only have 2 choices that can go into each spot on the display,
so we would have r=2

Answer 3

i'm not sure which notation works best for you, maybe
9 P 2 or
P(9,2)..