There are There are 100 photos in the envelope, among whose is the wanted one. Tim picks up 10 photos randomly. What is the probability that the wanted one is among these ten photos?

My Solution: I would say, since we have ONLY 1 wanted photo and we pick 10 photos therefore the probability that the photo Tim wants is one of those 10 is

C(1,100) / C(10,100)

My friend says : No! It's (C(1,1) * C(9,99)) / C(10,100)

which one is correct and WHY? Thank you