Problem:
A poll shows that of all voters approve of the mayor's work. On three separate occasions a pollster selects a voter at random. What is the probability that on exactly one of these three occasions the voter approves of the mayor's work?
Answer Choices:
A.
B.
C.
D.
E.
Solution:
The responses on these three occasions, in order, must be , or , where indicates approval and indicates disapproval. The probability of each of these is , so the requested probability is .
The problems on this page are the property of the MAA's American Mathematics Competitions