Any possible solutions to the following probability puzzler? Cheers A site with a rotating workforce provides emergency response training for some regular members of staff. In an emergency they are called into the emergency team. On the site 20% have emergency training. I want to find 3 emergency trained staff, and the contact list is out of date. What is the probability of getting 3 emergency trained staff after 3 phone calls. What is the probability of getting 2 after 3 calls?