Question

You own 19 CDs. You want to randomly arrange 9 of them in a CD rack. What is the probability that the rack ends up in alphabetical order?
The probability that the CDs are in alphabetical order is ?

Answer 1

we must assume that each CD's name begins with a different letter
number of ways to arrange 9 of 19 items
= P(19,9)
= 19x18x17x16x15x14x13x12x11
= 3.3522... x 10^10
so only one of these is in the correct order

prob(correct order) = 1/3.3522 x 10^10
= appr 2.98 x 10^-11

Answer 2

18.8