the blood bank at a hospital has a supply in which 5 or the

the blood bank at a hospital has a supply in which 5 or the 100 units have been contaminated with HIV. A patient recieves 3 units. What is the probability that all of these units are clean?

Solution

There are 100C3 ways to choose any 3 units, and 95C3 ways to choose 3 clean units.

Hence,

P(All clean) = 95C3 / 100C3 = 0.855998763 [answer]