Question

Anytime a child throws a Frisbee, the child’s dog catches the Frisbee with probability p,
independent of whether the Frisbee is caught or any previous throw. When the dog catches
the Frisbee, it runs away with the Frisbee, never to be seen again. The child continues to
throw the Frisbee until the dog catches it. Let X denote the number of times the Frisbee is
thrown.
(a) What is the probability mass function ??(?)?
(b) If p=0.2 , what is the probability that the child will throw the Frisbee more than four
times ?

Answer 1