Page 25 - Probability Demystified

14 CHAPTER 1 Basic Concepts

PRACTICE

1. A recent survey found that the ages of workers in a factory is distrib-
uted as follows:

Age Number
20–29 18
30–39 27
40–49 36
50–59 16
60 or older 3
Total 100

If a person is selected at random, find the probability that the person is
a. 40 or older.
b. Under 40 years old.
c. Between 30 and 39 years old.
d. Under 60 but over 39 years old.
2. In a sample of 50 people, 19 had type O blood, 22 had type A blood,
7 had type B blood, and 2 had type AB blood. If a person is
selected at random, find the probability that the person
a. Has type A blood.
b. Has type B or type AB blood.
c. Does not have type O blood.
d. Has neither type A nor type O blood.
3. In a recent survey of 356 children aged 19–24 months, it was found
that 89 ate French fries. If a child is selected at random, find the
probability that he or she eats French fries.

4. In a classroom of 36 students, 8 were liberal arts majors and 7 were
history majors. If a student is selected at random, find the probability
that the student is neither a liberal arts nor a history major.
5. A recent survey found that 74% of those questioned get some of
the news from the Internet. If a person is selected at random, find
the probability that the person does not get any news from the
Internet.