Question 891173
There are 20 quarts of milk on a supermarket shelf.
4 of them are spoiled.
That means 16 good and 4 bad.


A customer buys 3 quarts of milk.


Total possible samples that are different from each other is given by the formula of C(20,4) = 20! = 4845


Total possible samples that contain exactly 2 quarts of bad milk are equal to C(4,2) * C(16,1) = 6 * 16 = 96


Total possible samples that contain exactly 3 quarts of bad milk are equal to C(4,3) = 4


Total possible samples that contain at least 2 quarts of bad milk are equal to C(4,2) * C(16,1) + C(4,3) = 96 + 4 = 100


C(n,x) = n! / ((n-x)! * x!)


For Example:


C(4,2) = 4! / (2! * 2!) = 4*3*2*1 / 2*1*2*1 = 6


C(16,1) = 16 * 15! / (1! * 15!) = 16 / 1 = 16.


C(4,3) = 4! / (1!*3!) = 4*3*2*1 / 1*3*2*1 = 4