According to the Information Please Almanac, 80% of adult smokers started smoking before turning
18 years old. Suppose 25 smokers 18 years old or older are randomly selected and the number of
smokers who started smoking before 18 is recorded. Notice that this meets the criteria for a binomial
experiment.
(a) (2.5 points) Find the probability that exactly 20 of them started smoking before 18 years of age.
(b) (2.5 points) Find the probability that fewer than 15 of them started smoking before 18 years of
age.
