1.

There are 20 quarts of milk on a supermarket shelf, four of which are spoiled. A customer buys three quarts of milk. (a)How many samples are possible? (b)How many samples contain exactly two quarts of spoiled milk? (c)How many samples contain at least two quarts of spoiled milk?

2.

Without doing any computation, explain why C(11, 4) + C(11, 5)= C(12, 5). Hint: Suppose that a committee of size five is to be chosen from a pool of 12 people and John Doe is one of the people. How many committees are there that include John? How many committees are there that dont include John?