Question

Kindergarten class has 7 Scooby Doo , 8 Sesame Street, and 9 Barney DVDs. Each week, the class randomly selects 2 DVDs to watch on Friday. What is the probability that both movies are Barney?
Scott
there are 24C2 ways of selecting two movies

there are 9C2 ways of selecting two Barney movies

the probability is ... 9C2 / 24C2