Page 62 - Probability Demystified

CHAPTER 3 The Addition Rules 51

Summary

Many times in probability, it is necessary to find the probability of two or
more events occurring. In these cases, the addition rules are used. When the
events are mutually exclusive, addition rule I is used, and when the events are
not mutually exclusive, addition rule II is used. If the events are mutually
exclusive, they have no outcomes in common. When the two events are not
mutually exclusive, they have some common outcomes. The key word in
these problems is ‘‘or,’’ and it means to add.

CHAPTER QUIZ

1. Which of the two events are not mutually exclusive?
a. Rolling a die and getting a 6 or a 3
b. Drawing a card from a deck and getting a club or an ace
c. Tossing a coin and getting a head or a tail
d. Tossing a coin and getting a head and rolling a die and getting an
odd number
2. Which of the two events are mutually exclusive?
a. Drawing a card from a deck and getting a king or a club
b. Rolling a die and getting an even number or a 6
c. Tossing two coins and getting two heads or two tails
d. Rolling two dice and getting doubles or getting a sum of eight

3. In a box there are 6 white marbles, 3 blue marbles, and 1 red marble.
If a marble is selected at random, what is the probability that it is red
or blue?

2
a.
5
1
b.
3
9
c.
10
1
d.
9